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THE AMERICAN NATURALIST [Vol. XL VI 



winter and spring. It is probable that in its native haunts 

 the crayfish behaves differently. 



In the spring the males die off in great numbers. This 

 is a phenomenon which is noted in many arthropods, and 

 seems to be a wise provision of nature to prevent the now 

 useless males from using up the food required for the 

 spawning females and the young crayfish. Some of the 

 males, however, live to a good old age. I have found 

 several that were over 90 mm. long. 



In the case of C. hartnuins hartnui there are two more 

 or less well-marked spawning seasons, fall and spring. 



The fall laying, as indicated by females brought into 

 the laboratory, is during the latter part of September and 

 all through October and November. The spring laying 

 extends from about March 15 to about May 15. 



Andrews observed the process of laying in Cambarus 

 affinis. For four or five days previous to laying, the 

 female cleans her abdomen diligently and is exceedingly 

 sensitive to disturbances during that time. The actual 

 laying is done in deep water at night. It takes from ten 

 to thirty minutes to extrude the two hundred to four 

 hundred eggs. Each egg is attached by a tiny filament to 

 the abdominal hairs (9). 



The time of fertilization is supposed to be when the 

 eggs are laid, as they pass over the annulus ventralis. 

 Andrews found that on the removal of the annulus before 

 the eggs were extruded, the eggs were unfertilized and did 

 not develop. 



"When first extruded the eggs are almost black, but as 

 development goes on they become reddish in color and at 

 the end of about four weeks, when the young crayfish are 

 hatched, they are nearly transparent. The time of devel- 

 opment, from the extrusion of the eggs till the crayfish are 

 detached from the parent, is about eight weeks in the 

 species which I studied. 



Even after the young are detached from the swimmerets 

 of the mother, for several days they do not venture far 

 from her, and taking warning at any apparent danger, 



