THE AMERICAN NATURALIST [Vol. XLIII 



she became quiet and was soon in copulation. If we ex- 

 amine Table I it will be seen that in experiments 1 and 6 

 the same male copulated first in four of the trials, but in 

 experiments 2, 4 and 5 the male which copulated first in 

 trial 1 was equalled or excelled by the rival male in the 

 three succeeding tests. No female copulated first in all 

 four trials. 



In all the observations cited no evidence was seen which 

 would go to show any power of sex descrimination in the 

 crawfish. During the mating season the instinct of the 

 male is to grasp and turn over every crawfish which 

 comes in his way. The method is one of trial and the 

 result of such random movements depends largely upon 

 the reactions of the individual with which copulation is 

 attempted. If this individual is a female of the same 

 species the attempt may meet with success but if it is a 

 male or a female of another species the effort at sexual 

 union is usually of short duration. The lack of dis- 

 criminative ability on the part of the males is shown by 

 the fact that they often attempt to copulate with indi- 

 viduals of their own sex. This fact in itself is not of 

 course very conclusive as similar behavior is often ob- 

 served in many higher animals, such as dogs and cattle, 

 in which the males are doubtless able to recognize the 

 females as such. Furthermore, on two occasions males 

 were observed to be in copulation with females which had 

 been dead for twelve hours and in another instance a male 

 of one species (Cambarus virilis) was found in copulation 

 with a dead female of another species (C. blandingi acu- 

 tus). This last observation is of especial interest for, as 

 Andrews 5 says (p. 474) it is not known " whether the 

 male stylets and the female annulus are closely adjusted 

 to each other in each species or not. Experiments should 

 at least decide whether the males of one species can fill 

 the annuli of other species or not." The observation 

 just cited shows that two different species can at least 



•Andrews, E. A., « The Annulus Ventralis," Proc. Boston Soc. Natur. 

 Hist., Vol. 32, 1906, No. 12, pp. 427-479, pi. 43-48. 



