76 ME. W. a. EIDKWOOD ON THE HTOBEAJiTCHIAIi 



pushing the wet finger across a pane of glass. On referring to 

 the structure of the larynx, it is evident that the sound must be 

 produced by the vibration of the arytenoid cartilages or the edges 

 of the glottis, since there are no vocal cords. Judging by the 

 similarity in the shape of the arytenoids in the two sexes, it is 

 probable that there is but little difference ia the voices of the 

 male and female. 



Laeyfgeal MusciiEs OF Xenopus Icevis. 



In view of the fact that the laryngeal skeleton is so dissimilar 

 in the male and female of the two genera of the Anura Aglossa, 

 it is not surprising that the muscles in relation with it should 

 also differ in a remarkable degree. The following pages contain 

 an account of the laryngeal muscles of both sexes of Xenopus and 

 of the female JBipa. The specimens of male Pipa at my disposal 

 were all unsuited for an examination of the muscular system, 

 but I regret this the less as, thanks to Grronberg, our information 

 on the laryngeal muscles of the male Pipa is not deficient. The 

 object of this portion of the investigation was not only one of 

 correlation of the various muscle-masses occurring in the two 

 sexes of the same species, and of comparison of the muscles of 

 Pipa with those of Xenopus and the tongued Anura, but of the 

 search after additional evidence of the homology existing between 

 the parts of the laryngeal complex of the two aglossal forms and 

 those of the hyobranchial and laryngeal skeleton of more normal 

 batrachians. As has already been pointed out by Henle (19. 

 p. 24i), muscles running normally from the hyobranchial skeleton 

 to the larynx become in Xenopus and Pipa intrinsic laryngeal 

 muscles, owing to the annexation by the larynx of a part of the 

 hyobranchial skeleton. And some of the trunk muscles attached 

 in other Anura to the hyobranchial skeleton here become 

 extrinsic laryngeals. 



The first account of the laryngeal muscles of Xenopus we owe 

 to Mayer (26. p. 30). His description, which refers to the male, 

 is unaccompanied by illustrations. Henle followed, four years 

 later, with observations on the female, giving figures of the 

 intrinsic muscles of the larynx. Beddard has recently described 

 the muscular anatomy of both Pipa (1) and Xenopus (2) in greater 

 detail than had been done previously ; but he does not allude to 

 the laryngeal muscles of either genus. The information furnished 

 recently by Wilder concerning the laryngeal muscles of Xenopus 



