CRAYFISH. 293 
and becomes thicker in its passage through the genital 
ducts. It is possible that the genital ducts represent 
modified nephridia, and that the cavities of the gonads 
are coelomic. 
The ovaries are like the testes, but more compact. The 
eggs are liberated into the cavity of the organ, and pass out 
by short thick oviducts opening on the second pair of 
walking legs. As they are laid they seem to be coated with 
the secretion of the cement glands of the abdomen, and the 
mother keeps her tail bent till the eggs are glued to the 
small swimmerets. 
Fic. 146.—Female reproductive organs of crayfish, — 
After Suckow. 
ov., Ovaries ; ov’., fused posterior part ; od., oviduct ; vz., female 
aperture on the second walking leg. 
Before this, however, sexual union has occurred. The 
male seizes the female with his great claws, throws her on 
her back, and deposits the seminal fluid on the ventral 
surface of the abdomen. The fluid flows down the canal 
formed by his first abdominal appendages, and these seem 
to be kept clear by the movements of the next pair, which 
are also modified. On the abdomen of the female the 
agglutinated spermatozoa doubtless remain until the eggs 
are laid, when fertilisation. in the strict sense is achieved. 
The Development has been very fully worked out, and is of interest 
in being direct, without the metamorphosis so common among the 
