33. The anterior opening of the alimentary canal to the exterior is 

 through the gill slit in larvae 1 mm. in length, i. e. long before the 

 mouth is formed. The first food enters through this gill slit. The food 

 current before the fish can swallow is kept up by a very highly ciliated 

 gullet which extends from behind the gill region to near the hind gut. 



34. The mouth does not appear till the larva has increased 3 mm., i. e. 

 to a length of about 4 mm., and during all this time the hyobranchial gill 

 slit functions as mouth. There is here found a condition similar to the 

 one supposed by Dohrn to explain the replacement of the annelid mouth 

 by a gill mouth. 



35. Just in front of the notochord and near the region of the hyo- 

 branchial slit a strand of hypoblast cells extends up from the median por- 

 tion of the alimentary tract to above the notochord. This strand of hy- 

 poblast cells lies in the region where Dohrn supposes the annelid .esopha- 

 gus to have disappeared. 



3<>. The hind gut soon becomes enormously enlarged and later a large 

 number of long villi are developed. 



37. The larva- retain as an ancestral trait a large yolk sack, the yolk 

 being quite minute. The sack is largely taken up by the large pericardi- 

 um through which the long tubular heart extends from below and behind, 

 upward and forward. 



38. In conclusion: The tish in almost all its stages has become highly 

 specialized. Many stages resemble very closely primitive conditions but 

 the conditions can probably in but few cases be looked upon as a simple 

 reversion. Its development has, on the other hand, become extremely 

 ichth vized and its eg» stands at the end of the chain of eggs in which 

 the Braniliiostoma egg, the Elasmobranch eg£ and the normal fi?li egg fon>- 

 links. 



Ox birds ix Western Texas and Southern New Mexico. By A. W. Butler. 



Some rem u*ks regarding the embryology of amphiuma. Bv 0. P. Hay 



