II.] THE CRAYFISH AND LOBSTER. 235 



central masses (gangliform bodies) which stain 

 deeply. 



A zone of pigment is deposited at its outer 

 border. 

 L. Development. 



1. Examine the under surface of the body of a living 

 female "in berry." 



a. The fertilized ova ; each is attached to the setae 

 which fringe the swimmerets, by a delicate peduncle. 

 Make an incision into one : the ovum will be 

 liberated; the peduncle will be seen to be deriva- 

 tive of an egg-capsule which remains behind (a secre- 

 tory product of the abdominal wall and swimmerets 

 (cement glands of) cf. p. 186. 



b. Examine the thoracic sterna ; aggregates of filiform 

 whitish bodies (spermatophores) will in all proba- 

 bility be found adherent to the hinder ones, having 

 been deposited by the male. 



Tease one up ; it consists of a bundle of sperma- 

 tozoa, enclosed in a dense milk-white sperm- 

 capsule (a secretory product of the vas deferens. 

 Cf. Sect. G. i b.). 



Spermatophores may frequently be found project- 

 ing from the reproductive orifices of the male, if 

 killed during the breeding season. 



2. Remove the developing ova from time to time from 

 the body of the parent, and dissect off their egg-cases 

 with a couple of needles. Transfer to picric acid 

 solution and harden in alcohol. Look for 



a. The segmenting ovum (oosperm). Examined under a 



low power, its exterior appears slightly granulated. 



Imbed and cut sections; stain with carmine. Note 



a. The food yolk ; aggregated centrally, and chiefly 



