630 



Chas. B. Wilson 



considerable importance, and its failure under adverse circumstances 

 results fatally. 



The first sign of ciliation in these Amblystoma embryos consists 

 of a backward movement along the neural folds on the posterior 

 surface, just as in Eana. The two figures given in figs. 15 and 16 

 are camera lucida drawings of normal embryos showing the currents 

 generated by the cilia after the neural folds have closed (fig. 15), 

 and again twelve hours later (fig. 1 6). The cilia are confined chiefly 

 to the head, neck, and side of the body. Their motion can be 

 plainly seen under a good handlens, and the currents are easily 

 made out with the aid of a little chalk dust or other light colored 

 insoluble powder sprinkled in the water. In the earlier stage (fig. 15) 

 the strongest current starts from the dorsal surface jast behind the 

 head and sweeps backward and downward around the side of the 

 neck to the ventral surface just outside the heart. 



It thus covers exactly the position occupied in later development 

 by the gills. Another current starts from the anterior extremity of 

 the head and moves backward along the ventral surface until it 

 joins the first near the heart. The two then divide and pass back- 

 ward in a broad band along either side of the body to the posterior 

 extremity, broadening gradually as they go. A third current seems 

 to be a portion of the second, which separates from it on either 

 side just below the eye and circles around the latter. 



In the later stage (fig. 16), the current which passes across the 

 position of the future gills continues to be the strongest. But now 

 it unites with it's fellow from the opposite side, and the two, joined 

 by the second current which maintains it's former position, proceed 

 backward along the ventral surface. The whole side of the body 

 is covered by a very broad and comparatively feeble current which 

 takes its origin at the dorsal surface just behind the neck and runs 

 backward along the side of the body, bending toward the ventral 

 surface just before it reaches the posterior extremity. 



The ciliation of these Amblystoma embryos thus resembles very 

 closely that given by Assheton for Eana and the Newt, Triton 

 cristatus, especially in the strong current passing over the position 

 of the future gills. This fact serves to emphasize still further his 

 conclusion that its function is respiratory. 



With reference to the currents about the stomodeum I was unable 

 to determine anything definite save that such currents do exist. 



