CEUSTACEA 



109 



nucleus. The spermatozoa are made up into packets or 

 spermatophores in the vas deferens. 



Female. The ovary also consists of two long lobes extend- 

 ing forwards on each side of the stomach to the green gland, and 

 backwards to the second segment of the abdomen. The two 

 lobes are joined near the middle, and just posterior to the 

 junction give off the delicate oviducts which open on the basal 

 segment of the third pereiopod. Pairing takes place at the 

 period of ecdysis of the female, and the ova then are immature. 

 The spermatophores are retained in the spermatheca until the 



| Oviduct 

 3rd pereiopod 



Ovary 



5th pereiopod \ Testes 

 Vas deferens 



FIG. 52. Nephrops. Reproductive organs : A, female ; B, male ; 

 C, a spermatozoon greatly magnified. 



ova are ready to be extruded. The latter are fertilised when 

 they reach the brood chamber formed by the abdomen, and 

 its appendages. The sperms are attached to the egg by the 

 three neck processes, which contract, forcing the head into 

 the ovum. The eggs are attached to the setae of the endo- 

 podites. The setae pierce the outer envelope of the egg, and 

 the envelope forms a string of attachment. The fertilised 

 ova measure 1 5 mm. in diameter. 



Nephrops is liberated from the egg, after several months 

 of embryonic life, as a larva with thirteen pairs of appendages, 

 all but the abdominal appendages being formed. Such a 

 larva is called a zoea. The pereiopods are furnished with 

 the exopod, or swimming branch, and these are reduced to 



