352 A. W. BELLAMY. 



gested that " the data indicate that polarity in the egg arises . . . 

 in response to external conditions, viz., to the blood supply of the 

 egg: that region of the oogonium chancing to be most richly 

 supplied with arterial blood being destined to become, by virtue 

 of this respiratory and nutritive relation, the animal pole of the 



egg-" 



It may be stated here that the problem was by no means con- 

 sidered solved and in 1919 plans for its further and, more com- 

 plete investigation were fairly well worked out. The investiga- 

 tion has continued with numerous interruptions and is still 

 incomplete, but pending its outcome it has seemed desirable to 

 make this statement. 



It now appears that the previous observations were not suffi- 

 ciently extensive to warrant the general statements indicated 

 above. Certainly there is a considerable range of variation from 

 what I thought was the typical situation and 'illustrated in Fig. 3 

 of the 1919 paper. And, it may be added, the figure is correct. 

 But, on the other hand, cases have been observed more recently 

 where the vegetative hemisphere was largely supplied by arterial 

 blood, as well as various intermediate conditions. Furthermore 

 one occasionally finds in the vessels that run to the follicle in the 

 mature or nearly mature egg, a direct shunt between the small 

 artery and vein. As far as the existence of any definite relation 

 between the polarity of the mature or nearly mature egg and ar- 

 terial or venous blood supply is concerned, I am obliged to with- 

 draw the suggestion as it first appeared. It seems evident enough 

 that polarity must be established early in the history of the egg, 

 possibly in relation to the vascular supply. Supposing, as a work- 

 ing hypothesis, that such is the case it is conceivable that the vas- 

 cularization in the follicle may change considerably especially as 

 the egg approaches maturity the only stage previously examined. 

 It is along these lines that the investigation is being continued 

 with the hope of throwing further light on the question. 



