16 HISTORY OF THE EGG FROM FERTILIZATION TO CLEAVAGE. 



Whether any of the movements connected with the formation of the 

 disc can he properly characterized as " amoeboid " is a question that we 

 are unable to answer. The disc with its inflowing currents is certainly 

 something very unlike an amoeba with outstretched pseudopodia. There 

 are certain resemblances to be sure; but when we reflect on the ends 

 towards which the movements are directed in the two cases, we find 

 reason to suspect that the movements themselves may be determined by 

 unlike causes. The purpose of polar concentration in the fish egg seems 

 to be to bring the active protoplasm within the reach of cleavage, and 

 we certainly have no satisfactory evidence that this act is comparable 

 with the contraction of an amoeba. 



5. Polar Globules. — We have given above a brief account of the 

 appearance of the polar globules under what we consider to be normal 

 conditions. We have not met with any case of more than two globules, 

 and have never seen either globule undergo division. That such a 

 division may occur is not to be questioned, but it probably cannot be 

 of very frequent occurrence in the eggs we have studied. 



We have now to describe what see ins to be an abnormal event, — 

 the exit of the first polar globule through the micropyle. This has happened 

 but once in our experience, and then in the case of an artificially fertilized 

 egg. We have seen the polar globules probably not less than a hundred 

 times in eggs that were fertilized in the sea, and invariably within the 

 egg membrane. Ryder (No. 3, p. 10) states that he has never seen the 

 polar globules expelled through the micropyle. Several times we have 

 succeeded in getting the eggs from the sea to the laboratory in time to 

 follow the formation of both polar globules. The micropyle is usually 

 found at this time without much difficulty, as its position is a little to 

 one side of that of the polar globules. The retreat of the formative pole 

 frui, i the egg membrane always precedes the appearance of the first polar globule. 

 By the time the polar globule comes fairly into sight, the perivitelline 

 space has a depth not less than three or four times the diameter of the 

 globule. Obviously the globule does not and cannot pass through the 

 micropyle, or become lodged in it under such conditions. 



Hoffmann (No. 6, p. 68) has seen the first globule expelled through the 

 micropyle; and he holds that this is a normal occurrence, and that the 

 o-lobule lodged in the mouth of the micropyle bars the entrance of 

 supernumerary spermatozoa. One of us has made a single observation 



