. The biology of the amphibia. Amphibians. 382 THE BIOLOGY OF THE AMPHIBIA species. Have all reflexes and instincts been gradually modified in this way during phylogeny? In the ontogeny of Ambystoma, Coghill showed that the growth of certain axons and dendrites a fraction of a millimeter changed a helpless individual into one capable of exploring its environment. Similarly, in phylogeny, we should expect totally new behavior patterns to arise fully formed as the result of small morphological changes of the nerve patterns. Nevertheless, some reflexes and instincts have remained relatively stabl

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. The biology of the amphibia. Amphibians. 382 THE BIOLOGY OF THE AMPHIBIA species. Have all reflexes and instincts been gradually modified in this way during phylogeny? In the ontogeny of Ambystoma, Coghill showed that the growth of certain axons and dendrites a fraction of a millimeter changed a helpless individual into one capable of exploring its environment. Similarly, in phylogeny, we should expect totally new behavior patterns to arise fully formed as the result of small morphological changes of the nerve patterns. Nevertheless, some reflexes and instincts have remained relatively stabl
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Image ID: RHK74W
. The biology of the amphibia. Amphibians. 382 THE BIOLOGY OF THE AMPHIBIA species. Have all reflexes and instincts been gradually modified in this way during phylogeny? In the ontogeny of Ambystoma, Coghill showed that the growth of certain axons and dendrites a fraction of a millimeter changed a helpless individual into one capable of exploring its environment. Similarly, in phylogeny, we should expect totally new behavior patterns to arise fully formed as the result of small morphological changes of the nerve patterns. Nevertheless, some reflexes and instincts have remained relatively stable during evolution, while others, such as the unken reflex, have been gradually modified. Since the walk- ing reflexes have arisen from the swimming reflex pattern by individuation of parts during ontogeny, the same phenomena of individuation might be expected to account for the origin of new reflex patterns from a more generalized behavior pattern during phylogeny. Defense Reaction.—One of the most complete studies of the phylogenetic change in a behavior pattern in Amphibia has been Fig. 132.—The defense-fight reaction of Bufo calamita. {After Hinsche.) made by Hinsche (1928). Most Salientia when annoyed will inflate their lungs and bow their heads, assuming a defensive attitude. The inflation increases the size of the body and removes all wrinkles from the skin. Smooth, swollen frogs are both difficult to seize and difficult to swallow. Some toads add to this defense reaction several aggresive movements. The limbs are stretched, bringing the body clear from the ground, and then the whole body is brought forward in a butting reaction (Fig. 132). At the same time, the Spade-foot Toads may give a "fright cry," and frogs may scream with open mouths. Apparently, Cera- tophrys and Leptobrachium carinense add effective biting move- ments to this chain of reactions. There is no doubt that both the defensive and offensive components of this series of events. Please note