400 DAVIDSON BLACK 



by these animals of a musculature which is unrepresented in 

 urodeles. Rather would the nucleus in question appear to 

 be the direct expression within the central nervous system of 

 opisthoglossal anurans of the peculiar specialization of certain 

 muscles (i.e., m. genio-glossus and m. hyo-glossus) which in 

 other amphibians are more primitively arranged. 



Kallius (32) has shown that the anuran tongue in develop- 

 ment is primarily muscular and secondarily glandular, while 

 in the urodele tongue the reverse is the case. In both orders 

 the genio-glossus and hyo-glossus muscles are represented, but in 

 anurans these muscles develop within the substance of the tongue 

 to form a relatively complex intrinsic prehensile rnechanism. 



According to Gaupp (28) the genio-glossus muscle, by means 

 of its specialized arrangement, is responsible for the complex 

 , protractor and forward rotator prehensile movements ol the 

 frog's tongue, while the hyo-glossus muscle is concerned only 

 in the relatively simple act of retraction of this organ. On 

 the other hand, among urodeles the genio-glossus muscle is 

 primarily developed as a mechanism to aid in the prompt secre- 

 tion of the tongue glands and not to produce movements of 

 the whole organ. For this reason in origin, insertion and in 

 disposition of fibers the intrinsic tongue musculature of urodeles 

 is more simply arranged than in the frog (Kallius, 32). ^ 



For the first time in phylogeny the tongue in certain amphib- 

 ians (e.g., Rana) has become developed as a muscular pre- 

 hensile organ. Further, a definite sub-nucleus (the dorso-mediai 

 cell group) appears within the motor segment from which the 

 tongue musculature receives its innervation only in those ajn- 

 phibians in which the intrinsic prehensile muscle complex is 

 highly developed (e.g., opisthoglossal apura;ns). It is therefore 

 reasonable to regard the dorso-medial cell group of Rana as a 



^ I do not know whether the intrinsic musculature of the tongue in Spelerpes 

 is relatively more highly developed than in other urodeles, and I have been un- 

 able to find an adequate description of the tongue mechanism of this form in the 

 literature at my disposal. It would appear, however, that aside from the spe- 

 cialized protractor and retractor mechanism, the action of the intrinsic tongue 

 musculature does not play such an important role in prehension as does the 

 viscid glandular secretion of this organ. 



