. The Biological bulletin. Biology; Zoology; Biology; Marine Biology. TYPES OF NEPHRIDIA IN NEMERTEANS 209 PHYSIOLOGY OF THE METANEPHRIDIUM The process of excretion by this type of nephridium is presumably accomplished by the withdrawal of waste-containing fluids from the surrounding gelatinous parenchyma, and thus indirectly from the nearby blood, by means of the ciliary action of the nephrostome. These fluids then pass to the convoluted tubule, the cells of which are specialized for the excretion of additional waste materials or for the absorption of any contained nutrients, or both; after w

- Image ID: RHMT7Y
. The Biological bulletin. Biology; Zoology; Biology; Marine Biology. TYPES OF NEPHRIDIA IN NEMERTEANS 209 PHYSIOLOGY OF THE METANEPHRIDIUM The process of excretion by this type of nephridium is presumably accomplished by the withdrawal of waste-containing fluids from the surrounding gelatinous parenchyma, and thus indirectly from the nearby blood, by means of the ciliary action of the nephrostome. These fluids then pass to the convoluted tubule, the cells of which are specialized for the excretion of additional waste materials or for the absorption of any contained nutrients, or both; after w
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Image ID: RHMT7Y
. The Biological bulletin. Biology; Zoology; Biology; Marine Biology. TYPES OF NEPHRIDIA IN NEMERTEANS 209 PHYSIOLOGY OF THE METANEPHRIDIUM The process of excretion by this type of nephridium is presumably accomplished by the withdrawal of waste-containing fluids from the surrounding gelatinous parenchyma, and thus indirectly from the nearby blood, by means of the ciliary action of the nephrostome. These fluids then pass to the convoluted tubule, the cells of which are specialized for the excretion of additional waste materials or for the absorption of any contained nutrients, or both; after which the remaining fluid is forced through the efferent duct to be discharged through the ne- phridiopore. The movement of the fluid in the convoluted tubule is doubtless facilitated by the slender flagella with which it is provided. The numerous granules and minute vacuoles in the cytoplasm of this part of the nephridium are indicative of its excretory function, as Strunk (1930) has recently demonstrated experimentally for Annelids. EXCRETORY SYSTEMS IN CEPHALOTHRIX SPIRALIS In another species of the genus, C. spiralls Coe (formerly considered specifically identical with C. lincaris Oersted of Europe) of the New England coast, the excretory system of the female is likewise of the metanephridial type. In the two sexually mature males of this species which were available for study, however, no metanephridia were found, the excretory system consisting of a pair of clusters of protonephridia situated on the median walls of the cephalic blood lacunae (Figs. 13, 15). The meaning of this apparent sexual dimorphism is by no means clear and will require further investigation on immature forms of both sexes. It may be remembered in this connection, however, that a somewhat similar condition prevails for the reproductive organs of some of the bathypelagic nemerteans, the males of which have only a few pairs of spermaries (and these are situated in the head), while the females are provide

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