280 TEXTBOOK OF ZOOLOGY 



In the case of Cayiibarus clarkii the adults retire to holes or bur- 

 rows at the water's edge during the summer. It is here that the eggs 

 are laid and carried by the female until after hatching; then the 

 young cling to her swimmerets. In late summer or fall, soon after 

 the young hatch, the adults become very migratory at night, particu- 

 larly in rainy weather. In this way they help to distribute the young 

 to new water holes. 



The female reproductive organs are composed of a bi-lobed ovary 

 located beside the pyloric chamber of the stomach and beneath the 

 pericardial sinus. During development the eggs appear in the ovary. 

 Two oviducts lead, one from each side of the ovary, to a genital pore 

 in the coxopodite of the third walking leg (pereiopod) of each respec- 

 tive side. The ova develop in follicles in the ovary. The maturation 

 divisions (oogenesis) take place here and, when mature, the eggs 

 break into the central cavity of the ovary, from which at the time of 

 laying, they pass out through the oviducts. The male reproductive 

 organs are composed of the bi-lobed testis located dorsal to the pyloric 

 stomach and ventral to the heart. Spermatogenesis takes place here 

 and mature spermatozoa are shed. The tubular vasa deferentia ex- 

 tend posteriorly and ventrally to open externally on the coxopodite 

 of each fifth walking leg. During copulation (mating) the sperm 

 cells are transferred by the two pairs of anterior swimmerets (pleo- 

 pods) of the male from the apertures of the vasa deferentia to the 

 annulus (seminal receptacle) on the ventral side of the thorax of 

 the female. Later, vv'hen the mature eggs are laid, they are likely 

 fertilized as they pass posteriorly in the groove between the legs on 

 the two sides of the body. The fertilized eggs are fastened to the 

 swimmerets by a secretion and appear much as small bunches of 

 shot-sized grapes hanging there. The later development continues 

 here, and they are aerated by movements of the swimmerets through 

 the water. 



Cleavage divisions follow over the surface of the eg^ and the em 

 bryo develops on one side of the mass. The body form with segments 

 and limb buds appears, and hatching occurs in from five weeks to two 

 months. The larvae grasp the swimmerets with their chela and re- 

 main with the mother for about a month. Two or three days after 

 hatching they pass through the first molt or ecdysis; that is, they 



