THE YPSILOID APPARATUS OF URODELES. 



26l 



muscle immediately anterior to the cartilage extend farther 

 medially than those of the rest of the muscle and may even be 

 inserted into the second myocomma in association with those of 

 the M. ypsiloideus anterior (Fig. 3, to). 



It should perhaps be emphasized that the entire musculature 

 of the ypsiloid cartilage, while in all cases strongly developed, 

 shows a considerable amount of individual 

 variation, as if the apparatus were one 

 of relatively recent origin and still in the 

 experimental stage of physiological adap- 

 tation. The most definite of the muscles 

 involved is the M, ypsiloideus posterior. 



In addition to the above described mus- 

 culature of the Cartilage ypsiloides, the 

 posterior portion of the stem of the car- 

 tilage forms the origin of the anterior 

 portion of the M. pubo-ischio-femoralis in- Fic " 3 Dorsal w ( i. ,. 



from within body cavity 



tennis. This muscle takes its origin mainly showingthe muscles attached 

 from the mid ventral line of the pubo- to the ypsiloid cartilage of 



ischium, and that portion which arises Diemyctyiusviridescens,K$* 



On the right side the ante- 

 from the ypsiloid cartilage extends be- . f ., A , , 



J* nor part of the M. pubo- 



tween the posterior ypsiloid muscle and ischio-femoralis intemus has 

 the transversalis (Figs, i, 2, and 3,/). been cut awa 7- Abbrevia- 



T* -, it.- -r / t < o/ tions not previously ex- 



2. Inton helveticus. 1 . albcstns, sa/a- 



plamed: /<?, the portion ot 



inandra jnacnlosa, Ainblystoma cpacinn, A. t h e transversalis inserted 



pnnctatllUl. Although representing dif- into the second myocomma; 



ferent subfamilies, these forms so closely ^ tb f portio1 : of lhe trans ; 



versahs which is inserted 



resemble Diemyctylm in the anatomy of into the yps ii oid cartilage, 

 the ypsiloid region that they may be 



grouped together in this comparison. The Tritons most closely re- 

 semble Diemyctylus, the correspondence part for part being almost 

 exact. Salamandra and the Amblystomas have a relatively less; 

 strongly developed external oblique, while the rectus abdominis is. 

 broader and more powerful and the internal oblique more strongly 

 developed. The differentiations in connection with the ypsiloid 

 cartilage (Fig. 4), are, however, practically the same as in 

 Diemyctylus. The M. ypsiloideus anterior presents less deviation 

 from the longitudinal course of the rectus abdominis, almost all 



