550 BULLETIN OF THE 



not been sufficiently emphasized. This unique feature is the coalescence 

 of the " areal corpuscle " of the external aster with the envelope of the polar 

 cell at its distal extremity. It is a pecuHarity which may perhaps be of 

 importance in two ways. It is possible that it will some time help to a 

 better understanding of the forces at work in the process of cell division, 

 and it may also be of importance in deciding what share the " areal 

 corpuscles " of the stellar figures take in the formation' of new nuclei. 

 0. Hertwig is, so far as I am aware, the only observer who has given any 

 representation of such conditions as I find in Limax. In the cases 

 especially of Nephelis and Hsemopis he ('77, Taf. I., II.) has figured the 

 tip of the spindle as lying at the surface of the egg, and he mentions 

 (p. 20) " ein dunkles Korn, die peripher gelegene Spitze der Spindel." 

 The figure referred to in this connection (Taf II. Fig. 3) is perhaps in 

 this particular the least satisfactory of all those given by Hertwig ; for 

 the " Korn," although represented as being " peripheral," is not in con- 

 tact with the outline of the polar globule. If the apex of the globule 

 were turned a little toward the observer, so as not to be seen exactly in 

 meridional section, the "Korn" might appear, as it does in his figure, at 

 some distance from the surface (i. e. from the outline), even if fused 

 with it. One hardly has the right to assume that so skilled an ob- 

 server could have mistaken the position of this conspicuous granule ; 

 otherwise I should conclude that in this case, as in a majority of the 

 eggs represented, the tip of the spindle (its " Korn ") was merged in the 

 envelope of the polar cell. That such is really the case in Limax I have 

 not the least doubt. Evidently, then, in the polar cell, the " areal cor- 

 puscle " tahes no part in the formation of the new nucleus. The question 

 naturally arises. In how far are the conditions realized in the polar 

 cell duplicated in the Qgg cell % If the areal corpuscle contains nuclear 

 matter, and is essential to the completion of the new nucleus, how can 

 it so completely fail to realize its true destiny in the polar cells % Al- 

 though I can consider the question hardly more than fairly stated, still 

 there are some features in the formation of new nuclei, already dis- 

 cussed, as well as certain facts concerning the place where these " areal 

 corpuscles " first appear, which lead me to think that it may not be 

 necessary to interpret the latter as nuclear substance. Such a view 

 might cause this peculiarity of the polar cells to appear less bizarre. 

 The relation of the centre of the external aster to the envelope of the 

 polar cell is certainly unlike its relation to that of segment spheres in 

 ordinary cell division ; for there is no case, however small one of the 

 products of segmentation, in which the centre of the aster approxi- 



