92 GARDINER. [Vol. XV. 



Evidently the formation of the second body is accomplished 

 with much greater rapidity than the first. Nor does this seem 

 strange when it is borne in mind that the formation of the 

 first maturation spindle involved action on a great nucleus, 

 of which some parts are apparently selected and some rejected, 

 and then the journey across half the diameter of the ovum, 

 before the anaphase can be accomplished, while in the forma- 

 tion of the second polar body the substance involved is small and 

 compact and no journey is necessary. Naturally, the process 

 takes less time, and while I much regret that the full process 

 of the reorganization has not come under my observation, the 

 vast number of ova which one might have to section before 

 finding the stages sought, presents too discouraging and unin- 

 teresting a piece of work to be contemplated. 



In sections which show the two polar bodies side by side, 

 and near them the female pronucleus, no trace of the archo- 

 plasmic cap is visible in the latter. The remnant of this 

 body and of the achromatic fibers has entirely vanished. 

 Instead we find a mulberry-like-looking object, composed of a 

 large number of separate vesicles, each containing a round 

 bullet-like granule of chromatin (Fig. 20). In this form it 

 begins to migrate toward the center of the ovum, toward which 

 the male pronucleus is also moving. During the passage it 

 grows enormously and completely changes its structure. The 

 collections of separate vesicles disappear and give place to a 

 mass of chromatin grains imbedded in a linin network, almost 

 indistinguishable except from its smaller size and absence of a 

 nucleolus from the egg nucleus from which the first matura- 

 tion spindle was formed. It is to be noted that the centro- 

 somes in this form disappear with the anaphase. 



Fertilization. 



In no section have I been so fortunate to find the sperm 

 head in the act of entering the ovum, though I have frequently 

 found it within the cytoplasm quite close to the surface. In 

 such cases the outline of the ovum at the point nearest to the 

 sperm head showed a marked protrusion. This presumably 



