52 BULLETIN OF THE 



I have made some measurements and comparisons between eggs half 

 a millimeter in diameter and those having a diameter of about two milli- 

 meters, which indicate that the number of the villi remains constant 

 during the period of growth from the smaller to the larger size. 



In an egg 0.5 "mm. in diameter there occur about 30 villi in a space 

 of 35 /a ; i. e. the villi are about 1.15 /a from centre to centre. In an 

 egg 2 mm. in diameter from the same ovary, treated in the same manner 

 and cut at the same time, the villi are 4.5 /x from centre to centre (com- 

 pare Plate V. Figs. 3, 4). Allowing for the growth of the smaller egg, 

 which at the larger size would have a diameter four times as great as at 

 first, it is evident that the interval for a villus would be four times 1.15 fi, 

 or 4.G (A, which agrees fairly well with the space (4.5 /x) actually occupied 

 by a villus in the larger egg measured. There are also other reasons 

 for believing that the villi do not increase in number after the egg has 

 reached a diameter of half a millimeter. If new villi were interpolated, 

 one would reasonably expect to find the younger ones shorter than the 

 older ones; but at no stage which I have seen is there any marked 

 difference in their lengths. 1 



In the larger eggs measured (2 mm.), the nuclei of the granulosa were 

 on the average about 14 /a apart, from centre to centre; i. e. there were 

 about three villi to the diameter of each cell. But in eggs about half a 

 millimeter in diameter (compare Plate VIII. Fig. 3, and Plate IX. Fig. 5) 

 it is to be seen that from six to fourteen villi correspond to the diameter 

 of a single granulosa cell. If there has been no change in the num- 

 ber of villi, it follows that the granulosa cells must have increased in 

 number at least fourfold between the half-millimfcter stage and the two- 

 millimeter stage. It is for this reason I contend that there is no con- 

 stancy in the numerical relations of villi and granulosa cells, and that 

 consequently it is improbable that the former are the product of the 

 latter. 



1 It is evident that there has been a corresponding increase in the diameter of the 

 individual villi during the growth of the ovum, for in the mature condition they 

 form a continuous layer, with little or no intervening substance. 



Eansom ('67) has claimed that the pore-canals of the zona radiata increase in 

 number during the growth of that membrane. If one were to disagree with me, 

 and to regard the markings which first appear at the surface of the ovum as the 

 incipient zona instead of the villous layer, he would be compelled to adopt Ransom's 

 view, for the intervals between the markings on eggs half a millimeter in diameter 

 (1.15 ju,) would become, unless there were interpolations, 4.6 fj. apart when the eggs 

 had increased to two millimeters in diameter. In order to reduce the intervals to 

 the condition actually found in the zona of the mature egg (1.4 n), the number of 

 pore-canals would have to be increased more than threefold ! 



