66 THE CRAYFISH [CH. II 



sternal portions of the anterior segments. These produce 

 a secretion whereby the eggs are glued to the parent's 

 body. The eggs are laid in November or December, and 

 at this period the female bends her abdomen forward, 

 somewhat into the position normal to that region in crabs, 

 so as to enclose a chamber whose dorsal and ventral 

 margins become fastened together by the above-mentioned 

 cement. The eggs are received from the oviduct into this 

 chamber and become attached by the cement to the fringes 

 of the swimmerets and other parts of the ventral surfaces 

 of the abdominal segments. Each egg has a short stalk 

 of attachment. Impregnation is effected by the male 

 throwing the female on her back and then pouring the 

 spermatozoa through the tubular appendages of his first 

 abdominal segment on to the margins of the oviducal 

 apertures and on surrounding regions. The second pair 

 of abdominal appendages of the male are during this 

 process worked to and fro in the cavities of the first, as 

 though thrusting the seminal fluid through them, or 

 endeavouring to keep them clear. The female with eggs 

 attached is popularly said to be "in berry." The water 

 around the developing young is renewed, and aeration 

 maintained by gentle swaying movements of the swim- 

 merets. 



The young crayfishes are hatched during the first 

 half of the ensuing summer, and, as so frequently in fresh- 

 water animals, are already far advanced in development, 

 having undergone at least one moult of the skin while 

 within the eggshell. ' In general form the young is not 

 strikingly different from the adult. The cephalothorax is 



