No. 473] EGG-LAYING OF CRAYFISH 



347 



laid in water so shallow that the animal could not cover its back 

 when crouching down as close to the bottom as possible. This 

 female carried on some turning movements after laying and after 

 forty-three days the eggs, apparently all of them, hatched out, 

 contrary to expectation. 



Some individuals, however, could not be forced to lay in the 

 day time even by numerous repetitions of the alternating condi- 

 tions. Such crayfish did not lay at all, yet when examined some 

 were found to have the ovaries full of large eggs. Others kept 

 for two months gradually resorbed the ovarian eggs. In such 

 ovaries the old eggs were reduced to isolated, irregular yellow 

 masses scattered throughout the ovary, while translucent new 

 and minute eggs filled in much of the space between the degen- 

 erated eggs. 



In the cases of egg-laying observed under the above forced 

 conditions the extrusion of eggs followed after a thorough cleansing 

 of the region that then secreted copious glaire. By the bending 

 of the abdomen there was then formed a chamber, or baskt't, 

 full of glaire, a sort of "incubatory pouch" wliicli rnrivrd ihc 

 eggs and in which they were made fast to the plo(>|)()(ls. i lie 

 way in which the tail-fan expands to close iu this pouch and the 

 part played by the glaire, or mucus, were well (lescril)e(l for Astacus 

 by Lereboullet in 1860 (Ann. Sci. Nat., zoo\., ser. 4, voh 14). 



Being thus provided with a basket full of glaire the female 

 after a few trials lies down upon her back, a most remarkal)le 

 position considering the energy with which such crustaceans 

 avoid it and escape from it at other times. The flexure of the 

 abdomen becomes so excessive that the telson is brouglit uj) a^ 

 far as the bases of the chehe, or even to half cover theni, and 

 thus the glaire is smeared over all the ventral surface of rlw thorax 

 near the oviduct openings upon the bases of the third, or niiddie, 



and th(»ii^h hud under watcT they are not laid into the water. 

 'Vhv (rradnal rchixation (.f the abdomen finallv uncovers the bases 



been put upon the the 



