SKELETON AND LAEYNX OP XENOPUS AND PIPA. 67 



smaller size of the body of the male. An extensive series of 

 measurements shows that the proportion between the length o£ 

 bronchus and the distance between the snout and cloaca is the 

 same — one-seventh — in both sexes. 



Htobranchial Skeleton op Pipa americana, Female. 



The first figures published of the hyobranchial skeleton of 

 Pipa are those of Breyer (4). These figures, correct as far as 

 they go, show, however, none of the details of the skeletal parts 

 lying towards the median line. Mayer (25), in his monograph 

 on Pipa, says very little about the hyobranchial skeleton, and 

 gives no figures of it. It is in his paper on Xenopus (26. p. 31) 

 that he mentions the absence in Pipa of the anterior or hyoideau 

 cornua — a fact previously noticed by Meckel (27. p. 229). 

 Henle's description and figure (19. Taf. 2. fig. 11) of the female 

 are the first upon which any reliance can be placed. Henle 

 agrees with Meckel and Mayer that the anterior cornua are 

 reduced, and states (p. 16) that they are only represented by 

 the pointed cartilage at the front o£ the hyobranchial skeleton. 

 Parker (33. p. 651) was the first to show that the hyoideau 

 cornua are present in the embryo. He does not figure the hyo- 

 branchial skeleton of the adult, but in the ripe young, just about 

 to quit the maternal pouches (PI. 60. fig. 7), this portion of the 

 skeleton has already acquired most of the characters of the adult. 

 A criticism of this figure will be found on page 110. The figure 

 furnished by Grronberg (18. p. 636, fig. A. iii.), although only 

 an outline text-figure, shows more accurately than any published 

 previously the relations obtaining between the hyobranchial and 

 the laryngeal skeleton in the female. 



On comparing the hyobranchial skeleton of the female Pipa 

 with that of Xenopus, one recognizes at once the large wings 

 (PI. 9. fig. 1, a), the greatly reduced basal plate («/^^^), and in 

 front of it the large foramen (Ji) through which the hyoglossal 

 muscles rise to be distributed to the mucous membrane of the 

 floor of the tongueless mouth. The basal plate and the thyro- 

 hyals (t) have entered into the formation of the floor of the 

 larynx ; the bronchi are elongated and are supported by bronchial 

 cartilages (Jr.). The hyobranchial skeleton terminates in front 

 in a tapering rod of cartilage (cJi.'), evidently the homologue of 

 the rod-like cartilage (PI. 8. fig. 1. ch.') which extends forwards 

 in front of the hyoglossal foramen in Xenopus, The foramen is 



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