No. 3.] 



DEVELOPMENT OF THE TOAD-FISH. 



499 



eter, and when the axis of the embryo was visible, that was 

 indicated by an arrow drawn across the same circle. 



The result of this experiment is seen by an examination of 

 the circles given in Fig. II. Of the twenty-three developing 

 embryos, three show coincidence of the axis of the embryo with 

 the first cleavage plane (Fig. II. 1, 2, 3). There is no case of 



13 



14 



15 



16 



17 



Fig. II. 



exact coincidence with the second cleavage plane. Fourteen of 

 the embryos have the head directed towards the right of the 

 first line of cleavage, the axis of the body being at an angle with 

 the first cleavage plane of from 30 to 70 . In the remaining 

 six the head was to the left of the first cleavage plane, the angle 

 varying as before. 



Stages of Cleavage. 



Dr. Brooks 1 has described a segmenting fish egg, which he 

 says is probably that of BatracJius tan. He does not figure 

 the two- or four-cell stages, but the arrangement of the cells 



1 Studies from Biological Laboratory, Vol. II. 



