100 AN ELEMENTARY TEXT-BOOK OF BIOLOGY. 



stiff processes, all curved in one direction, projecting from their 

 edges. The epithelial lining of the spermiducts is glandular, and 

 secretes a viscid fluid which hardens to form threads (spermato- 

 phores) in which the sperms are imbedded. 



(2) The female (B) possesses an ovary (ov, ov), similar in shape 

 to the spermary, and occupying a similar position, but larger and 

 broader. Its colour is reddish-brown, and its surface is raised up 

 into rounded projections of various sizes, caused by the presence 

 of ova. This is most obvious in the breeding-season, when the 

 ovary becomes considerably larger. Within it is a cavity on 

 either side into which ova project, and from which, near the 

 junction of the lobes, a short, wide oviduct (od) leads to the basal 

 joint of the second walking-leg (g.o). 



The ova are reddish-brown spheres about of an inch in 

 diameter, and enclosed in capsules, the ovarian follicles, which 

 project into the cavities of the ovary. The wall of a follicle is 

 constituted by a structureless membrane, underneath which is a 

 layer of simple epithelium. The large ovum consists of a vitelline 

 membrane, a vitellus containing a considerable quantity of food- 

 yolk, and a germinal vesicle with numerous germinal spots. The 

 ripe ova burst from their follicles, pass into the ovarian cavities, 

 and thence by the oviducts to the exterior. 



In the breeding-season (autumn) the male, by means of the two 

 pairs of copulatory abdominal appendages, deposit spermatophores 

 upon the posterior thoracic sterna of the female. Just before the 

 eggs are laid the abdomen of the female is flexed, and a glairy 

 secretion is poured out from the numerous cement-glands, probably 

 dissolving the substance which unites the sperms together. The 

 eggs are now passed out from the oviducts, fertilized, and each 

 of them enclosed in a sort of capsule formed by this secretion, 

 and fixed by a filament of the same substance to one of the 

 swimmerets. Some two hundred eggs, are thus attached, and 

 during the winter gradually develop, the movements of the 

 swimmerets keeping them surrounded by fresh water. 



9. The nervous system consists of a nerve-ring passing into a 

 ganglionated ventral cord, and of nerves connected with these. 

 The ring is thickened dorsally into a large cerebral ganglion (brain) 

 situated in the head between the origin of the eyestalks. It is 

 divided into lobes, which indicate that it is composed of at least 

 three pairs of ganglia fused together. A very long asophageal 



