144 A> RICHARDS. 



that in the trematode, Gyrodactylus , the chromatin goes into the 

 nucleolus during the resting stage. 



Synapsis. Whether or not chromatin actually comes from the 

 nucleolus, the nucleus in the early part of the growth period 

 acquires an abundance of chromatin and a spireme stage at 

 once ensues. The spireme, in contact with the nucleolus, de- 

 velops rapidly and becomes massed on one side of the nucleus 

 just as in the "bouquet" or "synapsis" stage of the first matura- 

 tion prophase. Although some time intervenes between this 

 and the prophase of the first oocytic division, I regard this as 

 probably a true synapsis. What seems to be conjugation of the 

 chromosomal loops occurs (Fig. 26) and all the characteristics 

 of a synapsis are present. Furthermore, precocious synapses are 

 not unknown (e. g., see Montgomery on Euchistus, '01). Be- 

 ginning in the medullary portion of the ovary, synapsis spreads 

 rapidly over the entire organ, involving nearly all the oogonia 

 at once, although they are in different stages in different parts. 

 At the same time the cytoplasm is increasing in amount but there 

 is no evidence of a causal relation between the two phenomena 

 except that they are synchronous. The nucleus is as a rule 

 excentrically placed and the "bouquet" is frequently found on 

 the side of the nucleus next to the greatest cytoplasmic mass, 

 but there are many exceptions to this arrangement. Following 

 the "bouquet" stage the spireme spreads throughout the nucleus, 

 loses its property of staining very densely and takes on the 

 appearance of the typical resting nucleus about to undergo ma- 

 turation. It remains in this stage for a relatively long period 

 during which yolk production is accomplished and the ovum 

 attains its full size. 



Yolk Production. -Yolk production rarely begins before the 

 "bouquet" stage has passed off. Usually upon the same side of 

 the nucleus as that where the "bouquet" occurred, but always in 

 a part where the cytoplasm is abundant, an area staining more 

 deeply than the rest of the cytoplasm is visible. "It is com- 

 parable to certain of the differentiations which have been called 

 yolk nuclei in other eggs and its appearance is followed almost 

 immediately by the formation of yolk granules which are con- 

 tained in the egg cell itself" (Child). Often two or more of these 

 yolk-producing areas are to be seen in the same ovum. 



