328 



THE CELL 



period, protrude a stalk-like (peduncular) process right up to the 

 surface of the intestinal epithelium (Fig. 165). This process has 

 a regular fibrillary (rodded) structure, as is always seen, when an 

 active exchange of material takes place in definite directions ; 

 it may, therefore, be considered to be a special nutrient apparatus 

 of the ovum. In this case, too, the germinal vesicle is always 

 situated in immediate contact with the base of the nutrient ap- 

 paratus. 



FIG. 164. 



FIG. 165. 



FIG. 164. Immature ovum of Actinia parasitica. (x 145 : after Korschelt, p. 47, Fig. 8.) 

 Fio. 165. Transverse section through the peripheral end and through the stalk of egg- 

 cells of Sagartia parasitica (after O. and R. Hertwig) ; from Korschelt, Fig. 10. The 

 striated stalk of the egg-cell has penetrated into the epithelium at the top of the figure. 



A similar condition is found in the tubular ovaries of Insects, 

 which are divided into germ compartments and yolk compart- 

 ments. In this case the germinal vesicle is either again placed 

 close to the yolk compartment, or, which is more interesting, it 

 extends towards this compartment numerous pseudopodic pro- 

 cessess, by which means it considerably increases its superficial 

 area in that region, where the absorption of material is taking 

 place. Here, too, the yolk in the neighbourhood of the germinal 

 yesicle begins to separate off numerous dark granules, which have 

 been derived from the nutritive cells. 



In most animals the ova are nourished by means of the follicular 

 cells. Thus Korschelt has found that, as long as the formation of 

 the yolk and chorion is proceeding, the nuclei of the follicular 

 cells in Insects are situated in immediate contact with that surface 



