10 AKT. 3. S. 1KEDA : CONTRIBUTIONS 



strict sense), and soon begins to move baek again, to what is 

 apparently its first starting point, by the gradual rotation of the 

 egg as a whole. 



At a certain stage of this rotation, the barely perceptible 

 neural plate may be seen in a vertical position with the future 

 head-end upward (Figs. 11 and 12), for the axis of the plate is 

 shorter than the diameter of the egg. Even in later stages, the 

 embryonic body does not lie in an exactly horizontal position but 

 always at certain angles of inclination to the horizontal axis of 

 the egg. 



The neural groove is, in most eggs, to be perceived in 40-50 

 hours after the egg-deposition, while the neural folds appear some- 

 what later, becoming distinct only 10-20 hours later according 

 to temperature. These folds are closely approximated one to the 

 other from their first appearance. 



As I have already stated in my former paper, the great 

 peculiarity in the development of this species is that the head as 

 well as the remaining parts of the body are up to certain late 

 stages flattened out on the spherical mass of the yolk. Accord- 

 ingly, the hyomandibular arches on both sides are strongly de- 

 pressed and situated along the latero- frontal sides of the head, 

 while the heart which usually appears below the head in anuran 

 eggs, is here situated in front of the same. The body of the 

 curved embryo is raised less than in other species and is so to 

 speak wedged into the yolk mass, along the posterior and dorsal 

 surface of the egg. All this reminds one strongly of what is 

 seen in the eggs of the Ganoid fishes. 



During the fifth day or the following night, the neural groove 

 is completely closed by the coming together of the neural folds. 

 At this stage (Fig. lö), there is around the closed blastopore a 



