OVUM IN THE CAPE AND NEW ZEALAND PEEIPATUS. 297 



The Formation of the Polar Bodies. 



The formation of both polar bodies takes place in the same 

 way, and the process is evidently one of perfectly normal indi- 

 rect nuclear division, there being no trace of the phenomena 

 described by van Beneden (4) in Ascaris megalocephala ; 

 but it is needless to discuss these further, since they have been 

 since contradicted by Carnoy (7) . One peculiar point is the 

 direction of the spindle, being parallel to the surface of the 

 ovum, and not at right angles to it, the result being that the 

 polar body does not lie immediately above but to one side of the 

 germinal vesicle. Whether this is a point of any importance I 

 am not able to state ; but so far as I have been able to deter- 

 mine, its direction does not exert any influence on the subse- 

 quent history of the ovum. In all cases, as far as I know, 

 which have been hitherto described, the spindle lies at right 

 angles to the surface, and consequently the polar bodies lie 

 immediately above the germinal vesicle. 



That the polar bodies have all the characters of true cells I 

 think there can be no doubt, since, as is shown in figs. 20 a, 

 h, the first polar body is exactly similar in structure to the 

 ovum itself, from which it difi'ers only in size. Both its 

 nucleus and the surrounding protoplasm possess all the cha- 

 racters of those of the ovum, and it is perfectly clear that not 

 only one end of the spindle but also the protoplasm round it, 

 are extruded in the polar body. 



Contrary to the account given by Fol (8) for Asterias 

 glacialis, the germinal vesicle, after budding off the first polar 

 body, passes through a resting stage, as is shown in figs. 19 and 

 20 a, and the end of the spindle does not become transformed 

 at once into a second spindle. 



The entire absence of polar bodies in P. novae-zealandise 

 militates against Weismann's (18) theory as to their meaning, 

 which is based on the hypothesis that two are found in all 

 fertilized, and one in parthenogenetic ova. It is possible that 

 they may have escaped my notice, but it seems hardly likely 



