XXVII REPRODUCTIVE ORGANS 343 



proximal podomere of the fifth leg, in the female on that of 

 the third. 



The spermary (Fig. 86, /) lies in the thorax, just beneath the 

 floor of the pericardial sinus, and consists of paired anterior 

 lobes and an unpaired posterior lobe. From each side goes 

 off a convoluted spermiduct or vas deferens {vd), which opens 

 on the proximal segment of the last leg. The sperms are 

 curious non-motile bodies produced into a number of stiff 

 processes : they are aggregated into vermicelli-like sper- 

 matop/wres by a secretion of the vas deferens. 



The ovary is also a three-lobed body, and is similarly 

 situated to the testis : from each side proceeds a thin-walled 

 oviduct, which passes downwards, without convolutions, to 

 open on the proximal segment of the third or antepenulti- 

 mate leg. The eggs are of considerable size and contain a 

 great quantity of yolk {see p. 256). 



Both ovary and testis are hollow organs, discharging their 

 products internally. Their cavities represent the coelome, 

 and their ducts are organs of the same general nature as 

 nephridia. The ova, when laid, are fastened to the setae on 

 the pleopods of the female by the sticky secretion of glands 

 occurring both on those appendages and on the segments 

 themselves : they are fertilised immediately after laying, the 

 male depositing spermatophores on the ventral surface of 

 the female's body just before oviposition. 



The process of segmentation of the oosperm presents 

 certain striking peculiarities. The nucleus divides repeatedly 

 (Fig. 89, A, nu), but no corresponding division of the pro- 

 toplasm takes place, with the result that the morula-stage, 

 instead of being a heap of cells, is simply a multinucleate 

 but non-cellular body. Soon the nuclei thus formed retreat 

 from the centre of the embryo, and arrange themselves in a 

 single layer close to the surface (b) : around each of these 



