REPRODUCTIVE ELEMENTS IN MYXINE GLUTINOSA. 63 



conclusion as to their nature; he describes the projection from 

 the granulosa as extending only through the external micro- 

 pyle as far as the inner surface of the external zona. But it 

 seems to me extremely probable that the thin thread and row 

 of granules above mentioned belong to the follicular epithe- 

 lium, and are originally continuous with the conical projection 

 of the granulosa. Thus the differences between the condition 

 in the egg of the smelt and in that of Myxine, are two : first 

 the projection from the follicular epithelium into the micro- 

 pyle in the smelt is a hollow cone, not a solid one as in 

 Myxine; secondly, the inner end of the micropyle in the smelt 

 is open. With regard to the latter point, the micropyle is 

 completely open in the later stages of the egg of Myxine, and 

 whether the micropyle is at first closed internally in Osmerus 

 is not known. It is probable that careful investigation would 

 show that in all Teleosteans whose ova possess a micropyle 

 that structure is produced by a projection of cells from the 

 follicular epithelium. 



It is at least possible that in all Vertebrates the micropyle 

 will be found on investigation to be produced in the same way 

 as in Myxine, namely, by the growth of a cellular process 

 from the follicular epithelium towards the vitellus while the 

 vitelline membrane is being formed. 



Amongst some specimens of Myxine sent to me in December 

 last I found some in which the ovarian eggs appeared older 

 than any I had examined before, the poles being more obtuse 

 and the transverse diameter greater than usual. These eggs 

 were 20 mm. in length. I cut series of sections through the 

 polar regions of some of these eggs, and one of these sections 

 passing through the protoplasmic pole is shown in fig. 4. 

 Several differences are seeu from this figure to exist between 

 the follicle of these older eggs and that shown in fig. 2. The 

 connective-tissue envelope is thinner; the follicular epithelium 

 has its cells arranged somewhat differently, the nuclei being 

 crowded towards the deeper surface. But the greatest diflference 

 of all is the presence in the epithelium of deep pits expanded 

 at the bottom, and corresponding to these, processes from the 



