DEVELOPMENT OF SPELERPES BILINEATUS 209 



Neurenteric canal 



I have not found any neurenteric canal in Spelerpes. It may 

 be ver}' t^jansitorj^ and have been overlooked. I have examined 

 carefully only a few sections which cover the period of fusion 

 of the posterior neural folds. The post-anal gut is readily enough 

 found, but it ends blindly against a solid mass of nerve tissue. In 

 one case, the cells of the neural tube for a short distance were 

 somewhat loosely united in the region in which one would expect 

 to find the canal. 



The neurenteric canal was overlooked in Triton for some time, 

 but Schanz ('87) succeeded in finding it. The way in which the 

 blastopore closes and the fact that the neural folds fuse in front 

 of the blastopore renders it probable that there is no neurenteric 

 canal in Spelerpes. 



PART 2. EXPERIMENTAL 



Introduction 



The experiments of H. V. Wilson in pricking frog's eggs sug- 

 gested to the writer that since the eggs of Spelerpes are white, 

 it might be possible to mark them in some way and so follow the 

 movements of the egg material. The season of 1905 was largely 

 spent in the attempt to find suitable methods. A large number 

 of things that might possibly produce a mark upon the egg 

 were tried. At the very end of the season, it was found that 

 the aniline dye, Nile blue sulphate, produced definite spots upon 

 an egg in which the neural folds were forming and moved with 

 them. The following season demonstrated its applicability to 

 the solutions of the problems under consideration, although it 

 makes a less stable mark on the upper hemisphere in cleavage 

 stages than was anticipated. In later stages this difficulty is 

 scarcely apparent. The reason for this became evident when it 

 was found that the stain had a strong affinity for the yolk granules, 

 leaving the protoplasm unstained. This is well shown by marked 

 eggs which have reached the formation of the neural folds. The 

 folds, if they happen to pass through a stained spot, lose much 



