Experiments on the Early Development of the Amphibian Embryo etc. 627 



of withdrawal of the yolk cells as upon individual peculiarities of 

 the pigment cells. 



6. It will be readily seen that a separate neuropore cannot be 

 formed in these embryos. Ordinarily when the sides of the blasto- 

 pore meet and fuse at the mid-line two openings are left, the anterior 

 of which is the neuropore. 



Here, however, as the blastopore gradually closes, the anus 

 always occupies its extreme anterior end and there can be no 

 opening in front of it. In the development of the Newt Jordan 

 shows »that the relative position of neuropore and anus cannot be 

 constant«, but that the latter »may lie in almost any portion of the 

 original mid-line through the blastopore « (29). Several figures are 

 given showing different distances between anus and neuropore, the 

 two being usually quite close together. All that separates them is 

 a varying length of the fused sides of the blastopore. In these 

 embryos the sides of the blastopore do not fuse and hence there is 

 nothing to separate neuropore and anus and the two coincide in one 

 common opening. 



The neuropore is ordinarily quite transitory and even in the 

 present slow development cannot be regarded as sharing this opening 

 very long. 



Is this fusion of neuropore and anus at the anterior border of 

 the blastopore of any significance in determining » whether this anterior 

 portion of the blastopore primitively opened freely, and has been only 

 secondarily caught in as the neurenteric canal by the precocious 

 closing of the medullary folds ?« (29) It is certainly quite suggestive. 



Experiments with Ringer solution i). 



A second lot of eggs was obtained on March 20*^ from pools 

 covered with ice a quarter of an inch thick. This lot included all 

 three kinds, Kana, Chorophilus, and Amblystoma. Two large bunches 

 of Kana eggs were still unsegmented while the remainder w^ere in 

 the gastrula stage. The Chorophilus and Amblystoma eggs were all 

 in the blastula stage. 



1) The Composition of Ringer Solution is: 



Normal salt solution (0.75%) 100 cc. 



Potassium Chloride solution (lo/o) 3 - 



Calcium Phosphate added to saturation. 



Archiv f. Entwickelungsmechanik. V. 41 



