108 BULLETIN OF THE 



December. Older eggs, obtained at the end of January, although only 

 slightly larger than the December egg (21 mm. long), presented a very 

 different appearance at the micropylar region. Cunningham says of the 

 latter : " The micropyle is somewhat narrower, and the cells present in 

 it at previous stages have disappeared almost completely, only a little 

 debris remaining. The micropyle seemed also in these ova to be open 

 internally, though of this point I am not absolutely certain. If there 

 is a membrane closing the inner end, it is an extremely thin one." 



Cunningham has shown conclusively, I believe, that the granulosa 

 has much to do with the modifications of the egg membrane in the 

 micropylar region, but there are several particulars concerning which 

 his description and figures leave me in a rather unsettled state of mind. 

 In the first place, the author does not seem to distinguish with sufficient 

 sharpness between a funnel-like region, which may be partly the re- 

 sult of an infolding of the membrane, and a passage through the mem- 

 brane, which I have called the micropylar canal. It seems to me possible 

 that his uncertainty as to whether the micropyle is closed at its inner 

 end at a late stage may be due to this fact. The disproportion between 

 the calibre of the " micropyle " and the size of the spermatozoa 1 is not 

 alluded to, but at once suggests to me that the structure in question 

 may be the equivalent of the micropylar funnel only. I should be quite 

 certain that it was so, were it not that the drawing of the latest stage 

 (Fig. 12) — which is not sufficiently explained — admitted two inter- 

 pretations. In this figure the whole passage is divided into two por- 

 tions of about equal length, but of very unlike calibre. The inner half 

 is a narrow canal with parallel walls, about one third of a millimeter in 

 diameter (actual size about 10 /a) ; the outer half is abruptly widened 

 to 6 or 8 mm. in diameter, and gradually increases toward the gran- 

 ulosa to 10 mm. (nearly 300 //, actual size). There are no granulosa 

 cells, however, in either portion of the passage. The almost flat-bot- 

 tomed outer half of the passage would appear to be the equivalent of 

 the micropylar funnel in bony fishes, and I should certainly have so 

 regarded it if Cunningham had not evidently considered the inner nar- 

 rower portion as a part of the " micropyle " of previous stages from 

 which the cells had disappeared, leaving " only a little debris." If the 

 author is right in this assumption, that the narrow part of the ap- 



1 In its narrowest place the " micropyle " of the author's Figure 3 is represented 

 as 5 mm. in diameter in the drawing, which, being magnified 280 diameters, makes 

 its actual diameter about 18 /x, whereas the actual diameter of the head of a sper- 

 matozoon (Fig. 14) is not over 7 yu. 



