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Regenerating limb Stock Photos and Images

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Regenerating limb Stock Photos and Images

This green linckia seastar, Linckia guildingi, is in the beginning stag of regenerating a lost limb, Hawaii. The lost arm may not be predation. They c Stock Photo
RM2R4FCEC–This green linckia seastar, Linckia guildingi, is in the beginning stag of regenerating a lost limb, Hawaii. The lost arm may not be predation. They c
Blood Stars (Henricia sanguinolenta) scavenging on substrate. New England (USA), North Atlantic Ocean Stock Photo
RMC7HATD–Blood Stars (Henricia sanguinolenta) scavenging on substrate. New England (USA), North Atlantic Ocean
Underside of a starfish arm washed up on shore. Stock Photo
RFHX6510–Underside of a starfish arm washed up on shore.
Amputated by a predator, tip of this day octopus, Octopus cyanea, tentacle showing clear signs of limb regeneration, Hawaii. Stock Photo
RM2HH89FR–Amputated by a predator, tip of this day octopus, Octopus cyanea, tentacle showing clear signs of limb regeneration, Hawaii.
This is a pearl sea star (Fromia monilis: 20 cms.), which is one of the most beautiful species of starfish. It has a large red central plate, the mouth being underneath this area. The five arms are covered by many smaller brightly coloured plates. Sea stars can grow a new limb if one has been eaten. Regenerating starfish, subjected to such predation, can often be seen with 3 or 4 arms. Moving by means of hundreds of hydraulically-controlled tube feet, they feed mainly on sponges and small invertebrates. At the top, there is part of a yellow featherstar (Oligometra serripinna). Egyptian Red Sea Stock Photo
RFPMHXE2–This is a pearl sea star (Fromia monilis: 20 cms.), which is one of the most beautiful species of starfish. It has a large red central plate, the mouth being underneath this area. The five arms are covered by many smaller brightly coloured plates. Sea stars can grow a new limb if one has been eaten. Regenerating starfish, subjected to such predation, can often be seen with 3 or 4 arms. Moving by means of hundreds of hydraulically-controlled tube feet, they feed mainly on sponges and small invertebrates. At the top, there is part of a yellow featherstar (Oligometra serripinna). Egyptian Red Sea
Comet: Severed arm of Porous starfish [Fromia milleporella] regenerating 5 new arms. West Papua, Indonesia. Stock Photo
RFMMD8KN–Comet: Severed arm of Porous starfish [Fromia milleporella] regenerating 5 new arms. West Papua, Indonesia.
Pair of Luzon Sea Stars, Echinaster luzonicus, each regenerating from a single arm, Ghost Bay dive site, Amed, Karangasem Regency, Bali, Indonesia, In Stock Photo
RM2R8T30X–Pair of Luzon Sea Stars, Echinaster luzonicus, each regenerating from a single arm, Ghost Bay dive site, Amed, Karangasem Regency, Bali, Indonesia, In
The Journal of experimental zoology . bincreases, the potency to form a limb. Their prqspective po-tency is, therefore, greater than their prospective significance.Regeneration, when it takes place, is usually perfect, thoughsubject to delay in a varying degree. The process of regeneration The actual process of regeneration has not been followed indetail, though some observations may be recorded here. The earliest case (R. E. 127-) which need be considered waspreserved six days after extirpation of the limb rudiment.The regenerating limb appears on the surface (fig. 10) as a 428 ROSS G. HARRIS Stock Photo
RM2AN8BYX–The Journal of experimental zoology . bincreases, the potency to form a limb. Their prqspective po-tency is, therefore, greater than their prospective significance.Regeneration, when it takes place, is usually perfect, thoughsubject to delay in a varying degree. The process of regeneration The actual process of regeneration has not been followed indetail, though some observations may be recorded here. The earliest case (R. E. 127-) which need be considered waspreserved six days after extirpation of the limb rudiment.The regenerating limb appears on the surface (fig. 10) as a 428 ROSS G. HARRIS
Northern Sea Star (Asterias Vulgaris) on algae. Gloucester, Massachusetts, USA. North Atlantic Stock Photo
RMC7HARK–Northern Sea Star (Asterias Vulgaris) on algae. Gloucester, Massachusetts, USA. North Atlantic
Comet: Severed arm of Porous starfish [Fromia milleporella] regenerating 5 new arms. West Papua, Indonesia. Stock Photo
RFMMD8KH–Comet: Severed arm of Porous starfish [Fromia milleporella] regenerating 5 new arms. West Papua, Indonesia.
Multipore Starfish [Linckia multiflora] regenerating new arms. West Papua, Indonesia. Indo-West Pacific. Stock Photo
RM2C0RDGR–Multipore Starfish [Linckia multiflora] regenerating new arms. West Papua, Indonesia. Indo-West Pacific.
. Journal of experimental zoology. VIII. xin XIV The Journal of Experimental Zoology, vol. hi, no. 4 Plate II XV-XVII—Torsion in the regeneration of the right cheliped. Dorsal view of fifth stage lobsters,showing different phases of the regenerating limb.XV—Regeneration, 5 days, dactylopodite {dc) outward and above the propodite (/r*). (Lobster No 3) 4.5XXVI—Regeneration, 12 days, biting plane of claw turned inward at angle of about 45° to its original position. (Lobster No 7) 4.5XXVII—Cheliped completely regenerated, 13.5 days. Lobster had Just moulted and the completetorsion of the cheliped Stock Photo
RM2AGE67W–. Journal of experimental zoology. VIII. xin XIV The Journal of Experimental Zoology, vol. hi, no. 4 Plate II XV-XVII—Torsion in the regeneration of the right cheliped. Dorsal view of fifth stage lobsters,showing different phases of the regenerating limb.XV—Regeneration, 5 days, dactylopodite {dc) outward and above the propodite (/r*). (Lobster No 3) 4.5XXVI—Regeneration, 12 days, biting plane of claw turned inward at angle of about 45° to its original position. (Lobster No 7) 4.5XXVII—Cheliped completely regenerated, 13.5 days. Lobster had Just moulted and the completetorsion of the cheliped
Northern Sea Star (Asterias Vulgaris) on algae. Gloucester, Massachusetts, USA - North Atlantic Stock Photo
RMC7HBN4–Northern Sea Star (Asterias Vulgaris) on algae. Gloucester, Massachusetts, USA - North Atlantic
The Journal of experimental zoology . 0. 11 Figs. 10 and 11 Embryos with regenerating limb buds, ventral view. XilO.i2, regenerating limb; iV, normal limb. Figure 10. Experiment R. E. 127—/sixdays after operation. Figure 11. Experiment R. E. 129 — , fifteen days afteroperation. tion of cells in situ rather than upon the continued crowdingtogether of cells from the surrounding regions. The ectodermalcovering of the new limb bud, as well as that of the originalone, is considerably thicker than the ectoderm of the neighboringregion of the trunk. A case (R. E. 115-) preserved at nine days shows si Stock Photo
RM2AN8BNC–The Journal of experimental zoology . 0. 11 Figs. 10 and 11 Embryos with regenerating limb buds, ventral view. XilO.i2, regenerating limb; iV, normal limb. Figure 10. Experiment R. E. 127—/sixdays after operation. Figure 11. Experiment R. E. 129 — , fifteen days afteroperation. tion of cells in situ rather than upon the continued crowdingtogether of cells from the surrounding regions. The ectodermalcovering of the new limb bud, as well as that of the originalone, is considerably thicker than the ectoderm of the neighboringregion of the trunk. A case (R. E. 115-) preserved at nine days shows si
Northern Sea Stars (Asterias Vulgaris) on algae at low tide. Gloucester, Massachusetts, USA. North Atlantic Stock Photo
RMC7HAW2–Northern Sea Stars (Asterias Vulgaris) on algae at low tide. Gloucester, Massachusetts, USA. North Atlantic
. The Biological bulletin. Biology; Zoology; Biology; Marine Biology. SHRIMP CI.AW ASYMMETRY 243 simultaneous autotomy. The regenerating limb buds at both sites were monitored daily and sketches were made that were subsequently categorized into a series of devel- opmental stages. The regenerating limb buds were also measured, in blind observations, under a dissecting mi- croscope with a calibrated eyepiece. To reduce the chance of damaging the very delicate limb buds by repeated han- dling, measurements were made at 3-4 day intervals. Even so, 11 of the 27 animals suffered damage to the buds a Stock Photo
RMRHMB6N–. The Biological bulletin. Biology; Zoology; Biology; Marine Biology. SHRIMP CI.AW ASYMMETRY 243 simultaneous autotomy. The regenerating limb buds at both sites were monitored daily and sketches were made that were subsequently categorized into a series of devel- opmental stages. The regenerating limb buds were also measured, in blind observations, under a dissecting mi- croscope with a calibrated eyepiece. To reduce the chance of damaging the very delicate limb buds by repeated han- dling, measurements were made at 3-4 day intervals. Even so, 11 of the 27 animals suffered damage to the buds a
Blood Star (Henricia sanguinolenta) travels across Algae Bed. Gloucester, Massachusetts, United States, North Atlantic Ocean Stock Photo
RMC7HATA–Blood Star (Henricia sanguinolenta) travels across Algae Bed. Gloucester, Massachusetts, United States, North Atlantic Ocean
. Analysis of development. Embryology; Embryology. Vertebrates 681 Table 31. Summary of the Major Histological Changes Occurring in the Adult Urodele Limb During a 28-Day Period of Regeneration (from Manner, '53) DAYS OF REGENERATION MAJOR HISTOLOGICAL OBSERVATIONS 1 Day The amputation wound is closed over by the migrating epidermal cells. 2 Days Numerous phagocyte cells are present in the wound area. The disintegration of cartilage begins. The continued migration of the epidermal cells to the distal end of the regenerating limb results in an accumulation of these cells at this point. 5 Days T Stock Photo
RMRNA16D–. Analysis of development. Embryology; Embryology. Vertebrates 681 Table 31. Summary of the Major Histological Changes Occurring in the Adult Urodele Limb During a 28-Day Period of Regeneration (from Manner, '53) DAYS OF REGENERATION MAJOR HISTOLOGICAL OBSERVATIONS 1 Day The amputation wound is closed over by the migrating epidermal cells. 2 Days Numerous phagocyte cells are present in the wound area. The disintegration of cartilage begins. The continued migration of the epidermal cells to the distal end of the regenerating limb results in an accumulation of these cells at this point. 5 Days T
Northern Sea Stars (Asterias Vulgaris) and a Common Starfish (Asterias rubens) at low tide. Gloucester, New England Stock Photo
RMC7HAT4–Northern Sea Stars (Asterias Vulgaris) and a Common Starfish (Asterias rubens) at low tide. Gloucester, New England
. The Biological bulletin. Biology; Zoology; Biology; Marine Biology. ECDYSES STIMULATED BY LIMB LOSS 229 DAYS TO AUTOTOMY OF LIMB BUDS DAYS TO ECDYSIS 60 ANIMAL NUMBER I 5 LIMB BUDS NOT REREGENERATED REREGENERATED 10 15 20 25 30. FiGL'KE 3. Effect of removal of regenerating limb buds on the duration of the premolt period of Gccarcinns. Molting preparations were initiated in 30 animals by limb removal and at some later date (Day 0 in this figure) regenerating limb buds were autotomized (L. B. A.). Animals were observed to the next ecdysis. The total length of the horizontal bar represents the Stock Photo
RMRHKTEH–. The Biological bulletin. Biology; Zoology; Biology; Marine Biology. ECDYSES STIMULATED BY LIMB LOSS 229 DAYS TO AUTOTOMY OF LIMB BUDS DAYS TO ECDYSIS 60 ANIMAL NUMBER I 5 LIMB BUDS NOT REREGENERATED REREGENERATED 10 15 20 25 30. FiGL'KE 3. Effect of removal of regenerating limb buds on the duration of the premolt period of Gccarcinns. Molting preparations were initiated in 30 animals by limb removal and at some later date (Day 0 in this figure) regenerating limb buds were autotomized (L. B. A.). Animals were observed to the next ecdysis. The total length of the horizontal bar represents the
. The Biological bulletin. Biology; Zoology; Biology; Marine Biology. ECDYSES STIMULATED BY LIMB LOSS 225. FIGURE 1. Specimens of crabs with regenerating limb buds, (a, b) Gecarcinus latcralis. (c) Callinectes sapidits and (d) L'cu piti/iut.r. Eiglit, 4, 6, and 6 walking legs were removed from animals (a, b) 45, (c) 3o, and (d) 20 days previous to the time of photography. normal. We have performed a series of experiments on (.iecarcnnis to compare the relative effectiveness of eyestalk extirpation and limh loss in inducing pre- cocious molts. We find that eyestalk removal leads to the most rap Stock Photo
RMRHKTG1–. The Biological bulletin. Biology; Zoology; Biology; Marine Biology. ECDYSES STIMULATED BY LIMB LOSS 225. FIGURE 1. Specimens of crabs with regenerating limb buds, (a, b) Gecarcinus latcralis. (c) Callinectes sapidits and (d) L'cu piti/iut.r. Eiglit, 4, 6, and 6 walking legs were removed from animals (a, b) 45, (c) 3o, and (d) 20 days previous to the time of photography. normal. We have performed a series of experiments on (.iecarcnnis to compare the relative effectiveness of eyestalk extirpation and limh loss in inducing pre- cocious molts. We find that eyestalk removal leads to the most rap
. The Biological bulletin. Biology; Zoology; Marine biology. CRAYFISH PROECDYSIS 161 Table I Stage designations assigned to premolt events in different crustaceans 1 2 3 4 5 6 7 8 9 10 11 Membranous layer present C4 C4 C4 Activation of epidermis & hepatopancreas Do Regenerating limb buds begin rapid growtli Do Gastroliths begin to be formed Do Do I'^pidermis separates from old cuticle Di'a D„ D2 Do Do Di New setae begin formation as epidermal Di Di' Di Di'a Di' Di' Di' C4 invagination New setal invagination reaches maximum Di Di" Di Di" Di" Di'" D2 depth All morphologic Stock Photo
RMRHM41N–. The Biological bulletin. Biology; Zoology; Marine biology. CRAYFISH PROECDYSIS 161 Table I Stage designations assigned to premolt events in different crustaceans 1 2 3 4 5 6 7 8 9 10 11 Membranous layer present C4 C4 C4 Activation of epidermis & hepatopancreas Do Regenerating limb buds begin rapid growtli Do Gastroliths begin to be formed Do Do I'^pidermis separates from old cuticle Di'a D„ D2 Do Do Di New setae begin formation as epidermal Di Di' Di Di'a Di' Di' Di' C4 invagination New setal invagination reaches maximum Di Di" Di Di" Di" Di'" D2 depth All morphologic
. Analysis of development. Embryology; Embryology. Vertebrates 679 of a skeletal element is left behind will this regenerate in its own right. Bischler ('26) showed that Wendelstadt's results were faulty, for when repeated in a large variety of experiments, she secured regeneration of both the free extremity and the skeleton. Milojevic ('24) thought he had determined a polarization of the materials in the blaste- ma. By interchanging the cap of fore and hind limb regenerating blastemas he found that during the first ten days the basal part nutritional conditions, the interaction of other syste Stock Photo
RMRNA17X–. Analysis of development. Embryology; Embryology. Vertebrates 679 of a skeletal element is left behind will this regenerate in its own right. Bischler ('26) showed that Wendelstadt's results were faulty, for when repeated in a large variety of experiments, she secured regeneration of both the free extremity and the skeleton. Milojevic ('24) thought he had determined a polarization of the materials in the blaste- ma. By interchanging the cap of fore and hind limb regenerating blastemas he found that during the first ten days the basal part nutritional conditions, the interaction of other syste
. The Biological bulletin. Biology; Zoology; Biology; Marine Biology. LUNGFISH REGENERATION 251 which time a pectoral regenerate would have been totally restored under well-fed circumstances, the regenerating pectoral of the fasting fish attaind a length of 30-35 mm, barely a third of the 87 mm removed. By 8 months, the new limb measured approximately 50 mm, or about 60% of its original length. Upon resumption of feeding, substantial weight gain accompanied accelerating growth in the original regenerate, and 3^ months later the limb was 100% restored. Figure 2 depicts the growth curves of rege Stock Photo
RMRHN7JD–. The Biological bulletin. Biology; Zoology; Biology; Marine Biology. LUNGFISH REGENERATION 251 which time a pectoral regenerate would have been totally restored under well-fed circumstances, the regenerating pectoral of the fasting fish attaind a length of 30-35 mm, barely a third of the 87 mm removed. By 8 months, the new limb measured approximately 50 mm, or about 60% of its original length. Upon resumption of feeding, substantial weight gain accompanied accelerating growth in the original regenerate, and 3^ months later the limb was 100% restored. Figure 2 depicts the growth curves of rege
. Anatomischer Anzeiger. Anatomy, Comparative; Anatomy, Comparative. In the following figures (Figs. 8—11) are shown those cases in which regeneration took place from outside of the breaking-joint. The third leg was cut off near the end of the fifth segment (counting the most distal segment as the first). As shown in Fig. 8 the missing part •of the leg is regenerating from the cut-end (Sept. 13—26). Four new segments make up the new limb, corresponding to those that were lost. In another experiment (Sept. 11—26) the leg had been cut off obliquely leaving a small part of the fourth segment at o Stock Photo
RMRN9H3F–. Anatomischer Anzeiger. Anatomy, Comparative; Anatomy, Comparative. In the following figures (Figs. 8—11) are shown those cases in which regeneration took place from outside of the breaking-joint. The third leg was cut off near the end of the fifth segment (counting the most distal segment as the first). As shown in Fig. 8 the missing part •of the leg is regenerating from the cut-end (Sept. 13—26). Four new segments make up the new limb, corresponding to those that were lost. In another experiment (Sept. 11—26) the leg had been cut off obliquely leaving a small part of the fourth segment at o
. The Biological bulletin. Biology; Zoology; Biology; Marine Biology. 250 ELIZABETH BABBOTT CONANT Fish #28 developed fungus infection and died, but growth was followed in the other two. OBSERVATIONS Regeneration during fasting A regenerating appendage in a well-fed lungfish kept in water passes through a period of wound healing (1-2 days), a latent period of 2-3 weeks, and then periods of first accelerating and then decreasing growth, with replacement complete after 3 4 months (Conant, 1970). The regenerating pectoral limb in the three fasting fish showed healing and latent periods roughly si Stock Photo
RMRHN7JX–. The Biological bulletin. Biology; Zoology; Biology; Marine Biology. 250 ELIZABETH BABBOTT CONANT Fish #28 developed fungus infection and died, but growth was followed in the other two. OBSERVATIONS Regeneration during fasting A regenerating appendage in a well-fed lungfish kept in water passes through a period of wound healing (1-2 days), a latent period of 2-3 weeks, and then periods of first accelerating and then decreasing growth, with replacement complete after 3 4 months (Conant, 1970). The regenerating pectoral limb in the three fasting fish showed healing and latent periods roughly si
. The Biological bulletin. Biology; Zoology; Biology; Marine Biology. "nt. Figure 7. Histogram of the percentage of crabs missing or regenerating 1. 2, 3, or 4 or more limbs in the Rhode River. Maryland, from 1986 to 1989. the Rhode River, 11-17% of the population were missing or regenerating a single limb, while injury to two ap- pendages occurred less frequently (3-6%). Loss of three or more limbs was observed in less than 2.5% of the pop- ulation in the Rhode River for any given year (Fig. 7). The maximum number of limbs missing or regenerating on a single crab was six. The mean number Stock Photo
RMRHMX3Y–. The Biological bulletin. Biology; Zoology; Biology; Marine Biology. "nt. Figure 7. Histogram of the percentage of crabs missing or regenerating 1. 2, 3, or 4 or more limbs in the Rhode River. Maryland, from 1986 to 1989. the Rhode River, 11-17% of the population were missing or regenerating a single limb, while injury to two ap- pendages occurred less frequently (3-6%). Loss of three or more limbs was observed in less than 2.5% of the pop- ulation in the Rhode River for any given year (Fig. 7). The maximum number of limbs missing or regenerating on a single crab was six. The mean number
. The Biological bulletin. Biology; Zoology; Biology; Marine Biology. R LARGE 35] 559 30 25 20 15. 1986 1987 1988 1989 YEAR Figure 5. Between-year comparisons of percentages of crabs missing, regenerating, and both missing and regenerating limbs in the Rhode River by size from 1986 to 1989. Years with the same superscripted letter did not differ significantly in total autotomy frequency (STP tests. < 0.006). At North Inlet, juvenile crabs showed anoma- lously high levels of limb loss (44%) compared to adults (25%). Season. The percentage of injury for large crabs and for combined size class Stock Photo
RMRHMX4T–. The Biological bulletin. Biology; Zoology; Biology; Marine Biology. R LARGE 35] 559 30 25 20 15. 1986 1987 1988 1989 YEAR Figure 5. Between-year comparisons of percentages of crabs missing, regenerating, and both missing and regenerating limbs in the Rhode River by size from 1986 to 1989. Years with the same superscripted letter did not differ significantly in total autotomy frequency (STP tests. < 0.006). At North Inlet, juvenile crabs showed anoma- lously high levels of limb loss (44%) compared to adults (25%). Season. The percentage of injury for large crabs and for combined size class
. The Biological bulletin. Biology; Zoology; Biology; Marine Biology. 424 L. D. SMITH AND A. H. MINES. "nt. Figure 7. Histogram of the percentage of crabs missing or regenerating 1. 2, 3, or 4 or more limbs in the Rhode River. Maryland, from 1986 to 1989. the Rhode River, 11-17% of the population were missing or regenerating a single limb, while injury to two ap- pendages occurred less frequently (3-6%). Loss of three or more limbs was observed in less than 2.5% of the pop- ulation in the Rhode River for any given year (Fig. 7). The maximum number of limbs missing or regenerating on a sin Stock Photo
RMRHMX4E–. The Biological bulletin. Biology; Zoology; Biology; Marine Biology. 424 L. D. SMITH AND A. H. MINES. "nt. Figure 7. Histogram of the percentage of crabs missing or regenerating 1. 2, 3, or 4 or more limbs in the Rhode River. Maryland, from 1986 to 1989. the Rhode River, 11-17% of the population were missing or regenerating a single limb, while injury to two ap- pendages occurred less frequently (3-6%). Loss of three or more limbs was observed in less than 2.5% of the pop- ulation in the Rhode River for any given year (Fig. 7). The maximum number of limbs missing or regenerating on a sin
. The Biological bulletin. Biology; Zoology; Biology; Marine Biology. AUTOTOMY IN BLUE CRAB POPULATIONS 425 Table IV n/K nl expected versus observed frequencies ot mlacl cmhs and those missing or regenerating I. 2. J. nr 4 or more limbs in the Rhode River. Maryland from 1986 to 1989 Rhode River, Maryland 1986 1987 1988 1989 Iniurv status Obs. Exp. Obs. Exp Obs. Exp. Obs. Exp. Intact 1050 960 505 463 536 514 569 528 -1 Limb 234 369 75 138 86 122 78 145 -2 Limbs 83 64 26 18 20 13 34 18 -3 Limbs 21 6 12 -) 4 1 8 1 - >4 Limbs 12 0.5 4 0.7 3 0.4 3 0.1 G-test P < 0.001 P < 0.00 1 P < 0.0 Stock Photo
RMRHMX3K–. The Biological bulletin. Biology; Zoology; Biology; Marine Biology. AUTOTOMY IN BLUE CRAB POPULATIONS 425 Table IV n/K nl expected versus observed frequencies ot mlacl cmhs and those missing or regenerating I. 2. J. nr 4 or more limbs in the Rhode River. Maryland from 1986 to 1989 Rhode River, Maryland 1986 1987 1988 1989 Iniurv status Obs. Exp. Obs. Exp Obs. Exp. Obs. Exp. Intact 1050 960 505 463 536 514 569 528 -1 Limb 234 369 75 138 86 122 78 145 -2 Limbs 83 64 26 18 20 13 34 18 -3 Limbs 21 6 12 -) 4 1 8 1 - >4 Limbs 12 0.5 4 0.7 3 0.4 3 0.1 G-test P < 0.001 P < 0.00 1 P < 0.0
. The elements of experimental embryology. Embryology, Experimental; Embryology. 304 FIELDS AND GRADIENTS Amphibia. It has always been difficuh to connect this with any purely chemical specificity of the regenerating tissues at one level as against another level of the limb, and recent work has made such a view wholly untenable. For one thing we have the fact already referred to (p. 271) that the regenerated material is at first wholly undifferentiated, and is only later determined in relation to the substrate on which it grows. This is not conclusive, for it merely proves that the old tissues Stock Photo
RMRCNDYP–. The elements of experimental embryology. Embryology, Experimental; Embryology. 304 FIELDS AND GRADIENTS Amphibia. It has always been difficuh to connect this with any purely chemical specificity of the regenerating tissues at one level as against another level of the limb, and recent work has made such a view wholly untenable. For one thing we have the fact already referred to (p. 271) that the regenerated material is at first wholly undifferentiated, and is only later determined in relation to the substrate on which it grows. This is not conclusive, for it merely proves that the old tissues
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