No. 473] 



EGG-LAYING OF CRAYFISH 



349 



duct when the ovary was being removed. Both oviducts were 

 greatly distended, though for a long time only the right one had 

 been discharging eggs. 



The glaire into which the eggs come is dense along the edges 

 of the abdomen and can be picked up by forceps as ' blobs ' that 

 hang down a half inch or so, supporting their weight. But the 

 rest of the glaire is too weak and watery to be pulled away. When 

 the abdomen was forcibly bent back to examine this glaire and 

 the female prevented from laying for a night there was no second 

 secretion of glaire over laying though cleansing movements were 

 carried on again. When the crayfish laying eggs was suddenly 

 put into boiling water the glaire coagulated sufficiently to form 

 an opaque white mass over the eggs in the posterior part of the 

 abdominal basket but the glaire over the issuing eggs did not 

 become opaque enough to hide their red color. 



The transfer of the eggs from the oviducts to the pleopods 

 within the abdominal chamber is purely the work of gravitation. 

 Though the crayfish lies upon its back the abdomen is always 

 lower than the thorax and in some cases several legs were actively 

 braced against the bottom of the dish in a manner to exaggerate 

 this sloping of the body. In one case the animal sat propped up 

 at an angle of nearly forty-five degrees supported upon its short 

 fifth legs and upon the abdomen. Generally, however, only the 

 tip of one chela and one leg touched the bottom and thus gave 

 more stability to the animal as it lay upon its rounded back. 



The deep groove between the bases of the thoracic legs favors 

 the backward flow of the eggs which coming from each oviduct 

 unite in one stream that flows along the thorax onto the abdomen 

 and there divides to flow right and left along the bases of the 

 pleopods. W^hen, as is often the case, the animal lies with one 

 side higher up than the other the eggs coming out of the more 

 elevated oviduct drop some 6 to 8 mm. diagonally across the body 

 before reaching the sternal surface. In such positions also the 

 eggs accumulate in the lower side of the abdomen and when the 

 animal is taken in the hand the eggs will flow right and left in the 

 abdominal chamber as right or left is held lower. The glaire 

 is thus not dense enough to stop the movement of eggs except at 

 the edges of the chamber and upon the pleopods. Even after 



