380 



ZOOLOGY 



FIG. 190. 



PlG. 190. The metamorphosis of the Frog. (After Brehm.) Numbers indicate the sequence 



Questions on the figures. How much of the egg is really ovum? What are 

 the changes which take place in passing through the various stages? In what 

 order do the legs appear? How is respiration effected after stage 6? After stage 

 n? What is proven by the collecting of the tadpoles as shown in 3? How do 

 they retain their position. 



FIG. 191. 



FIG. IQI. Tailed Amphibians. From Nicholson, after Mi vart. A, Siren; B, Amphiuma[lridactyla; 



C, Necturus, 



Questions on the figures. Compare these three types and note all the chief 

 differences of external structure. Compare also with figures you may be able to 

 find of other Urodela. 



