44 BULLETIN OF THE 



The funnel^ as I shall call that portion of the egg membrane which 

 forms the walls of the depression, involves a modification of both the 

 zona radiata and the villous layer. Both are affected in two ways, in 

 thickness and in direction. 



The villous layer begins to grow thinner at some distance from the 

 edge of the funnel. Sometimes it retains its normal thickness to within 

 a distance equal to the diameter of the funnel ; at other times it begins 

 to grow thinner at three or four times that distance from the pit. Its 

 diminution in thickness is quite gradual and very nearly uniform until 

 it reaches a minimum at the micropylar canal. The stalks of the villi 

 are shortened more than the heads, in comparison with their appearance 

 on other parts of the capsule, and the boundaries between them grad- 

 ually become less distinct. The diameter of the villi also decreases 

 considerably. Near the bottom of the funnel they become very short, 

 but frequently it is evident that, instead of constantly diminishing in 

 diameter, they may even increase as compared with other regions of 

 the funnel (Plate VI. Figs. 5-8). 



In all parts of the funnel the villi retain a direction perpendicular to 

 the outer surface of the zona. In the lateral wall, and especially near 

 the bottom of it, they are slightly wedge-shaped or conical, the head 

 ends being narrower than the root ends. They thus accommodate them- 

 selves to the diminished space at their disposal (Plate VI. Figs. 6-8). 



The zona radiata (Plate IV. Fig. 1) likewise begins to diminish in 

 thickness at some distance from the micropylar canal, and continues to 

 do so until it reaches the canal ; but it does not, like the villous layer, 

 grow thinner at a uniform rate. Its thickness decreases very slowly to 

 within a short distance of the region where the membranes begin to bend 

 inward to form the funnel, and then it suddenly narrows to one third its 

 normal dimension, after which it again decreases more slowly until it 

 reaches the micropylar canal. The pore-canals are not perceptibly finer 

 nor more closely set in the vicinity of the micropyle than elsewhere. They 

 retain in most regions a rectilinear course perpendicular to the surface 

 of the zona, but at the region of most rapid reduction in the thickness 

 of the latter, and for a little distance on either side of it, their course 

 is curved, the concave side facing the micropylar canal. 



The change in the direction of the two layers of the egg-shell results 

 in the formation of an external depression, which is considerably deeper 

 than the total thickness of the shell, so that, even with a great diminu- 

 tion in the thickness of the latter, its inner surface projects into the 

 yolk as a conical elevation, which is nearly as high as the thickness of 



