ON THE DEVELOPMENT OF PARASITIC COPEPODS. 43 



dispersed as granules in a peripheral achromatic reticulum, as in 

 the oogonia (Fig. 3). Minute nucleoli appear in this reticulum. 

 The boundaries between the oocytes become so faint as to be no 

 longer everywhere perceptible. At the same time the cyto- 

 plasm begins to increase in volume and the diameter of the egg 

 cord to increase. This process continues until the egg cord 

 passes into the oviduct, and for some time thereafter. When 

 the oocytes have traversed about a fifth of the oviduct, the cell 

 boundaries reappear and the nucleus migrates to very near the 

 center, there forming an enlargement in the oocyte (Fig. 4). The 

 reticulum and the three to four nucleoli have grown considerably 

 with the growth of the nucleus. A few yolk spherules and fewer 

 oil globules appear and grow to considerable size. For some 

 time growth of the oocyte consists almost solely in the addition 

 of yolk spherules and oil globules and this continues until the 

 yolk almost obliterates the cytoplasm and closely surrounds the 

 nucleus. I have seen these spherules and oil globules separated 

 from the protoplasm with a high speed centrifuge (kindness of 

 Dr. Lyon), the former are heavier and the latter lighter than the 

 protoplasm. 



B. L<einai'gus uniricatus. The oogenesis resembles that of 

 the dichelestid. In the oogonial divisions there appear to be 

 sixteen chromosomes, but these are set so close together that I 

 cannot be sure by actual count. 



In the growth period the reserve materials, yolk and oil 

 globules, are laid down in ways that show them to be of quite 

 different consistency. The oil globules (dissolved out in sections) 

 appear as minute points that grow in size but always retain a 

 spherical shape. The yolk substances, at least some of them, 

 are laid down as thin discs. A disc receives new substance on 

 its flat surfaces only, and the layers of substances are alternately 

 chromatic and achromatic in staining qualities (when much de- 

 stained after certain stains). Some of these piles of discs become 

 spherical, others oblong by addition of more discs. The con- 

 stituent layers do not mix but remain separate until dissoved in 

 the segmenting egg or developing embryo. The oil globules 

 are relatively few in number and large in size. The yolk bodies 

 vary greatly in size, none of them reaching the size of the oil 

 globules. 



