548 BULLETIN OF THE 



studied with this point in view, and especially the presence of conditions 

 at maturation which appear to be, if at all comparable with, at least 

 fundamental modifications of this process, seem to preclude the exist- 

 ence of typical polar globules in a number of the groups of animals, 

 while the failure to find equivalents of the " canal cells " in the higher 

 phanerogams is possibly even a greater obstacle to the claim that they 

 are of universal occurrence. 



The fact that it is the eggs possessing a large proportion of nutritive 

 substance which deviate from the typical formation of polar globules 

 would indicate that it might be the accumulation of this food material 

 which interferes with the normal or more primitive method of matura- 

 tion, and prevents the formation of cell-like polar bodies. There seems 

 little doubt that the elimination of portions of the substance of the 

 germinative vesicle as described by Balfour for Elasmobranchs, by 

 Oellacher for bony fishes * and birds, and by Van Bambeke and Hert- 

 wig for Amphibia, represents in some hitherto unexplained manner the 

 formation of polar globules. It is perhaps safe to indulge the expecta- 

 tion that some of the representatives of these groups will ultimately 

 furnish the means of explaining how the two processes are reconcilable : 

 at present it does not seem possible to present a satisfactory hypoth- 

 esis of their mutual relationship. It can only be said that in all cases 

 there is probably an elimination of a part, and of only a part, of the 

 substance of the germinative vesicle together with a small portion of 



nection with the blastomere, which appears to be a trifle the larger, — just as in Clep- 

 sine the oral-ring substance does (compare Whitman '78", Fig. 15), — and which 

 takes the lead in the production of the small cells about the primary pole, exactly as 

 Whitman (Figs. 19, 20) has shown to be the case in the leech. That the ringlike 

 disposition of the substance is in no way a necessary feature follows from the con- 

 dition (Whitman, Fig. 70) presented by the " aboral ring." This, however, is no 

 argument for the identity of Grobben's body with polar rings, since the polar globules 

 sustain in Clepsine the same relation to the blastomere which leads in segmentation. 



Henneguy ('80) has also reported the discovery of polar globules in one of the 

 Crustacea (Oniscus). 



* p. S. — Hoffmann ('80) has given a preliminary account of the early stages of 

 several osseous fishes, in which he shows that a single polar globule is produced in 

 the noraial way from the external half of a maturation spindle. He claims, however, 

 that, as the nucleus which is formed from the inner half of this spindle is the 

 " Eikern," so the nucleus which is formed from the external half is the " Kichtungs- 

 kbrperchen." Can it be that this represents a transition from a process where the 

 production of polar cells entails the loss of a certain portion of the yolk to one where 

 there is an elimination of only nuclear material, or is it to be assumed that Hoffmann's 

 statement is, from its brevity, slightly inexact ? 



