SMALLWOOD. [VOL. II. 



by anything that corresponds to the " Hellerhof " of MacFar- 

 land and others. The sperm enters at the vegetal pole, though 

 not in any definite place. The tail is lost before the sperm 

 enters the egg membrane (Fig. i). The head is a solid body 

 having a distinct angle in the middle. If there is a middle- 

 piece, it is practically indistinguishable. The only indication 

 that I have found of such a body is that on one end of the 

 sperm head sometimes one finds a narrow band that stains a 

 little denser than the rest of the head. 



The sperm head becomes top-shaped as it begins to migrate 

 toward the animal pole with the point' leading. The head 



becomes elliptical (Fig. 3) and stains very 

 black. It remains in this solid form for 

 some time, while the first polar spindle is 

 passing from the metaphase until the ana- 

 phase of the second polar spindle. During 

 the anaphase of the second maturation, the 

 solid sperm head becomes vesicular, and for 

 FU;. 5 . - Late anaphase a ver y short time is accompanied by astral 



of second maturation 



spindle, centrosome rays. I have not been able to discover a 



still present. Cortical j rpusde in connection with the 



zone enlarging. The 



sperm is composed of aster, nor have I ever seen an amphiaster. 



three vesicles and ac- n 



bv astral At this same time secondary asters usually 



ravs. 



appear in the egg, which are smaller than the 

 sperm aster. As the chromosomes of the second polar spindle 

 begin to assume the vesicular form, the sperm aster disappears, 

 and the sperm, consisting of one or more vesicles, rapidly ap- 

 proaches the inner pole of the second polar spindle. When 

 the sperm consists of more than one vesicle, these fuse into 

 one when the aster disappears. While the vesicular sperm is 

 shifting its position it does not increase in size to any notice- 

 able extent, but as soon as it comes near the female pronucleus, 

 which now consists of but three or four vesicles, it rapidly 

 increases in size until it is about twice as large as it was when 

 migrating toward the animal pole. From the time that the 

 sperm head enters the egg until it comes to lie in contact 

 with the female pronucleus (Fig. 6), it is not attended, so far 

 as I have observed, by any body which might be taken for a 

 central corpuscle or a centrosome. 



