MUSEUM OF COMPARATIVE ZOOLOGY. 47 



"maturation spindle " was visible near the mieropylar pole (Plate IV. 

 Fig. 1). As there were no other granulosa cells left attached to the 

 egg, the first impulse was to regard this as one of the " polar cells " 

 formed by the ovum during maturation. This seemed the more prob- 

 able on account of the undoubted existence of a maturation spindle. 

 A serious obstacle to this view was the great size of the cell as com- 

 pared with the narrow mycropylar canal. Even the elongated condition 

 of the cell would hardly warrant the assumption that it had passed 

 through so narrow an orifice. The examination of suitable sections 

 from ovarian ova (Plate IV. Fig. 5, Plate V. Fig. 2, Plate VII. Fig. 2) 

 soon showed that this interpretation was inadmissible, and made it as 

 certain as one could expect, without having traced it from its origin, that 

 the cell in question was a specially modified granulosa cell. It may be 

 appropriately called the mieropylar cell, for, whatever may be its function, 

 the morphological fact remains that it occupies the mieropylar funnel, 

 and lies directly over the mieropylar canal. I have not been able to dis- 

 cover that its substance extends into the canal, but the number of favor- 

 able cases which I have examined is not enough to allow me to say that 

 such a condition is improbable. So far as I know, nothing of this kind 

 has been found in the case of any of the osseous fishes, unless the figure 

 given by Hoffmann ('81, Taf. I. Fig. 20) for Leuciscus is capable of 

 being thus interpreted. 1 Hoffmann himself has evidently not considered 

 the condition of the granulosa in the region of the micropyle sufficiently 

 important to give it any attention in the text, but there is not the least 

 doubt in my mind that the accumulation of granulosa cells which he 

 has figured is the equivalent of the granulosa plug in Lepidosteus. I 

 am inclined to believe, moreover, that Hoffmann has overlooked a real 

 difference between the cells in this region, and that an equivalent of the 

 mieropylar cell of Lepidosteus will be found in Leuciscus, and perhaps 

 in many other of the osseous fishes, especially in those where there is a 

 large mieropylar funnel. In fact the three cells which in Hoffmann's 

 figure (Plate I. Fig. 20) seem to occupy the funnel, are all slightly larger 



than the remaining granulosa cells, and one of them — the deepest 



fairly represents in its position the mieropylar cell. Since all the cells 

 have a somewhat diagrammatic appearance, it is not too much to expect 

 that a more careful examination would show a difference between them. 



1 Since this account was written, Owsjannikow and Cunningham have both 

 found similar conditions in other fishes. A review of their articles will be found 

 at the end of the historical section of the present paper, pp. 104-110. 



