No. 447-] BR E EDI AG HABITS OE CRAVEISH. 



That this crayfish grows in the open about at the rate above 

 indicated seems not improbable from the measurements made 

 upon 80 specimens of C. affinis taken early in October, 1903, 

 from a small pond in Baltimore that had been stocked a few 

 years before. Five of these were 85-100 mm. in lcn,<;th and 

 obviously belonged to a different period of life as there wcie 

 none between these and 65 mm. lengths. The remaining 75 

 ranged from 65 to 32 mm. There were only 6 below 40 and 

 12 above 56 ; the remaining 57 were from 40 to 56 mm. long. 

 Thus 76% were from 40 to 56 mm. long and we may believe 

 these were hatched that same Spring and were about 4 months 

 old ; the same would apply to the few smaller ones. The 12, or 

 16%, that were above 56 and not above 65 mm. long are too 

 small for young that had passed a second summer and probably 

 were of the same age as the majority. The five largest speci- 

 mens were too large for second summer crayfish and probably 

 were at the end of their third summer. The absence of any in 

 what we would regard as second year lengths may be jierhaps 

 connected with the draining and drying that the i)(>nd suffered 



Sexual maturity. — In rearing crayfish it was tound that then- 

 sexual instincts and organs mature long before tlie ma.ximum size 

 was attained. Some of the young represented in Tables I and 

 II were found to unite in. pairs in October when but 4.^ montlis, 

 or 141 days old. These very small crayfish, two niches long, 

 thus had their sexual instincts develoi)e(l. Moreox er the sperm 

 taken from the male is then, apparently, just like that ot the lull 

 grown males. The females i and 5 of the first table had sperm 

 plugs, though the other females did not. 1 hcse temales were 62 

 and 50 mm. long. The female Xo. 2 of the second table was 

 clasped by male No. 3 and subsequently had a sperm plug : this 

 female was 52 mm. long. Whetherthe.se females of 50, 52 and 

 62 mm. in length will lay eggs next spring remains to be seen. 

 The males seen to unite with females were 55 and 59 mm. long. 



The two females described in the last section when 70 and 79 

 mm. long and 22 months old were put with males April 10, 

 1903. Though they had been alone for some months they 

 at once were united with the males and the annulu> ol each 



