176 HUBERT DANA GOODALE 



the gastrula stage, but before an embryo has appeared, the ante- 

 rior wall of the gastrula has invariably broken out into a vesicle, 

 resulting in the stoppage of development. This indicates, per- 

 haps, a good deal of pressure by the invaginating macromeres 

 upon the anterior wall. After the neural groove begins to appear, 

 the embryo may be removed from the membranes without much, 

 if any injury. 



The egg before cleamge, ivith especial reference to the yolk granules 



A few hours after the egg is deposited, a number of small pits 

 (from 2 to 6) may be seen scattered over the upper hemisphere 

 of the egg. They may represent the entrance points of the 

 spermatozoa, since physiological polyspermy has been observed in 

 Urodeles by Jordan ('93), Braus ('95), Gronroos ('98) and others. 

 Later on, they all disappear but one. Whether this one is an 

 original pit, or has arisen meanwhile, I do not know. At an 5^ rate, 

 the one remaining persists until after the earlier cleavages. It 

 has been noticed by Jordan ('93) in Diemyctylus and by Eycle- 

 shymer ('95) in Amblystoma. It doubtless corresponds to the 

 fovea of Schultze. According to these authors, it contains the 

 polar bodies, but thus far I have been unable to find them, either 

 in the living egg or in sections. 



Preserved material shows a well-defined cap of lighter color than 

 the rest of the egg. This cap, which represents the more proto- 

 plasmic portions of the egg, is not cut by the first cleavage plane 

 in any definite direction. Vertical sections of such an egg, fig. 

 2a (drawn somewhat diagrammatically), show a well-defined 

 arrangement of the yolk material into zones. Corresponding 

 to the external light cap is a rather thin upper zone of finely gran- 

 ular material which extends well towards the equator, but does 

 not reach it. It decreases in thickness towards its edges. Be- 

 neath this is a zone of coarser yolk material. The rest of the egg 

 is composed of still larger yolk granules which often have a char- 

 acteristic longitudinal, median groove (fig. 2, e). These zones 

 are not sharply separated frojn one another nor are the yolk 

 granules characteristic of one zone found exclusively in that zone. 



