SOME POINTS IN THE DEVELOPMENT OF THE 

 TOAD-FISH {BATRACHUS TAU). 



CORNELIA M. CLAPP. 



The following observations were made during the summer of 

 1891, while studying, under the direction of Dr. C. O. Whitman, 

 at the Marine Biological Laboratory, Wood's Holl, Mass. 



The Blastopore. 



In examining the younger embryos of Batrachus tan, my atten- 

 tion was attracted to the appearance of the blastoderm, as seen 

 in Fig. I. c. The egg was placed in weak osmic acid, for a few 

 moments, when the outline could be clearly seen through the 

 egg membrane. 



Earlier stages were obtained, and treated in the same manner. 



Fig. I. a, represents the blastoderm at the time of the first 

 appearance of the axial thickening. 



Fig. I. b, shows the embryonic ring when the embryo is well 

 denned, and a little after the time when the notch first makes 

 its appearance. 



The point of special interest to be noticed, in these early 

 stages, is the form of the blastopore, and its closure at some 

 distance behind the embryo. 



In Fig. I. c, the two sides of the embryonic ring are seen to 

 approach each other, as they grow over the yolk, forming an 

 acute angle behind the embryo, and giving rise to a very con- 

 spicuous notch. 



In Fig. I. d, this notch is seen at a little distance behind the 

 embryo ; a shadowy connection may be traced between the germ 

 ring and the embryo. 



In later stages, this notch is seen to retreat farther behind 

 the embryo, as the thickened margins of the blastoderm unite, 

 and it disappears shortly before the completion of the closure 

 of the blastopore. 



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