482 STANLEY C. BALL 



make their appearance. As a result two or even more nuclei may 

 come to lie within one common yolk mass, which occupies the extreme 

 tip of the ovary. In other words, a syncytium is formed here. In 

 the vast majority of cases only two ova are involved so that the usual 

 picture displayed in this region represents a binuclated yolk mass. 



Patterson was evidently misled, both as to the relation of 

 the ova to the cells of the vitellaria, and their relation to each 

 other, by the phenomenon of oblique sections across thin mem- 

 branes. Hardly a better example of this condition could be 

 found than a longitudinal section of the Paravortex ovary, 

 particularly of its posterior end where it turns inward to meet 

 the oviduct. At this angle several of the ova are sure to be 

 cut with varying degrees of obliquity, rendering the egg mem- 

 branes correspondingly indistinct. The membrane between 

 the last two ova included is the most likely to be cut at the 

 sharpest angle, and hence the most difficult to observe. 



Since all the eggs in the ovary are flattened nearly perpendicu- 

 larly to the horizontal plane, a frontal section of the organ is 

 all that is necessary to prove that very distinct membranes 

 do exist between all ova, particularly at the posterior end of 

 the ovary (fig. 8). A vertical section cut obliquely through 

 the posterior angle of the ovary brings out the same fact. 



Patterson's figure, introduced as evidence in favor of his 

 syncytium theory, indicates very clearly to us that the ovary 

 curved inward at the right. The egg having the larger nucleus 

 was pressed into its neighbor containing the smaller nucleus. 

 Since the plane of the section was more tangential to the first 

 than to the second the former appears to be contained within 

 the boundaries of the latter. The membrane between the two 

 appears indistinct, not because it is undergoing degeneration, 

 as Patterson would interpret the condition, but on account 

 of the obliquity of the plane at which it is cut. Many of my 

 preparations present an identical appearance. 



In a similar manner I would account for the faintness of the 

 boundaries between ova and vitelline cells in the same figure. 

 Sections through the posterior end of the ovary and the over- 

 lying vitellaria are not usually pei'pendicular at all points to 



