XL. 



THE EMBRYOLOGY OF THE FROG 



THE GENERAL EMBRYOLOGY OF THE TADPOLE AS COM- 

 PARED WITH THAT OF THE CHICK 



As in our study of the embryology of the chick, it is essential that 

 the student again read the chapters on mitosis, fertilization, and the 

 summary on embryology, and then go over each system in the develop- 

 ing chick corresponding to the system he may be studying in the frog, 

 for only in this way can the comparison of the developmental processes 

 be understood. 



After this has been done, the following groups of Craniata must be 

 kept clearly in mind to make clear the various embryological relation- 

 ships which must be referred to, not only in the study of embryology, 

 but also in Comparative Anatomy. 



CLASSIFICATION OF CHORDATA 

 (After Newman) 



Sub-Phylum I. Cephalochordata (Adelochorda), (Fig. 312). 

 i. n. 





limit If {' 



MI M 1 



.<&' 



'Zr\ 



Fig. 312. 



I. Examples of Amphioxus ( Branchiostoma and Lancelet) , Tunicates (First 

 two upper figures), Lamprey (The large, lower, left-hand figure-adult; and the 

 embryo lamprey, usually called Ammocoetes 2 upper right-hand figures), and the 

 Hag fish (2 lower right-hand figures). 



II. Sketch of chief kinds of Urochordata showing distribution in sea. Dotted 

 lines on left indicate life-zones. The surface is called the pelagic zone. (From 

 Herdman.) 



This includes but a single family of fish-like creatures, of which 

 there are about twelve species. The type form is Amphioxus 

 more correctly known as Branchiostoma). 



