270 



INEZ L. WHIFFLE. 



_1 



sected show the ypsiloid cartilage well developed and with prac- 

 tically the same muscular attachments as in the adult. 



From my necessarily limited study of larval forms, it appears, 

 therefore, that (i) ypsiloid cartilage is of later origin than the 

 differentiation of the muscles associated with it, and (2) that it 

 arises as an unpaired structure in association with these muscles 

 and at a time when the girdle itself still exhibits its paired nature. 

 // cannot, therefore, be interpreted as having arisen from the epi- 

 pubic process, but must be regarded as an independent cliondrifica- 

 tion in association with differentiations of the innermost portion of 



tJic rectus abdominis muscle in 

 the two somites immediately an- 

 terior to the pelvic girdle. 



Larvae of both Spelerpes 

 and Desmognathus show, as do 

 those of lunged forms, an 

 early differentiation of the M. 

 ypsiloidcus posterior. As in 

 the adult lungless forms the 

 fibers of this muscle insert, in 

 the absence of the ypsiloid car- 

 tilage, into the linea alba of 

 the first somite. 



I had thought it possible that these larval stages might even 

 show a vestige of the ypsiloid cartilage itself, and there is, in 

 fact, some indication that such may be the case though I have as 

 yet been unable to obtain the stage necessary to absolutely prove 

 it. The union of the two halves of the pubis begins at the ex- 

 treme anterior end, thus forming the future median anterior proc- 

 ess of the pubis. This union (Fig. 9) appears to occur, not as 

 a direct fusion of the two halves by the process of chondrifica- 

 tion of the connective tissue between them, but rather by a fusion 

 of each half with a median unpaired anlage, which lies in the 

 linea alba anterior to the girdle. Thus in transverse section this 

 median portion shows no trace whatever of a paired nature, a 

 fact which is especially significant when the condition is compared 

 with that of Necturus larvae in which the median anterior process of 

 the pubis (Proccssus cpipubicus} shows a paired nature even to its 



FIG. 9. Ventral view of the pubo- 

 ischium of Desmognathus fusca larva (21 

 mm.) obtained by maceration, < 2 5- 

 Drawn with camera. Abbreviations : /, 

 femur ; /, lateral process ; m, median proc- 

 ess, at this stage the only median part. 



