Notes on the Development of the Newt 

 (Triton Cristatus). 



By 



Alice JoIinHoii, 



Demonstrator of Biology, Newnham College, Cambridge. 



And 



liilian Sbeldon, 



Bathurst Student, Newnliam College, Cambridge. 



With Plates XXIV, XXV, and XXVI. 



The present paper is a continuation of some observations 

 made by one of us on the early development of the Newt (14). 

 It was then shown that the blastopore of the embryo becomes 

 the permanent anus. 



The same discovery has since been made in the Frog by Mr. 

 Spencer (21), in Petromyzon by Mr. Shipley (20) j and in 

 Ceratodus by Mr. Caldwell (6). Dr. Gasser stated the same 

 fact with regard to Alytes obstetricans in 1882 (8), in a 

 paper with which the present writers bave only recently 

 become acquainted. 



The Post-Anal Gut. 



The existence of a post-anal gut in the embryos of many 

 Vertebrates appears at first sight an important argument 

 against the view of the identity of the blastopore with the 

 anusj because it would naturally be supposed that the blasto- 

 pore must be at the extreme hind end of the gut. We find, 

 however, that a post-anal gut is present in the Newt embryo, 

 and its relations there, as described below, explain this diffi- 



18 



