335 



thus confined to what is contained in von Ihering's notes upon this 

 subject, because, so far as I have been able to find out from the record- 

 ing papers, nothing more is written since 1892 concerning this que- 

 stion. The specimens which the last mentioned author has dissected 

 were males, and he says (p. 44) »tous les exemplaires, plusieurs douzai- 

 nes, que j'ai vus jusqu'à présent, étaient des mâles«. But he seems to 

 be doubtful whether Parastacus is hermaphrodite or not. In the col- 

 lection of animals recently brought home from Chile by Mr. Du sen 

 was a number of Parastacus. It is natural that I, when receiving them, 

 was much interested to learn the structure of the reproductive organs 

 of these animals, if possibly an examination of them would be able to 

 throw some more light on this question. I found then at once the co- 

 existence of genital »orifices« on the basal joints of both third and 

 fifth pairs of legs. The supposition expressed by Dr. von Ih ering- 

 seemed then at first, at least, possible, A closer examination revealed 

 however in the next instance that even exteriorly male and female 

 specimens could be discerned. The abdomen of the female Parastacus 

 is namely a little broader and its pleura more laterally directed than 

 in the male. This can be made out by a comparative measurement in 

 the following way. In the female the greatest width of the third ab- 

 dominal somite is about as great as the distance from the posterior 

 margin of the ocular emargination of the carapace to the cervical 

 groove measured in a straight line and in the horizontal plane from 

 the former point. 



In the male again the greatest width of the same abdominal so- 

 mite is always less, and sometimes considerably less than the 'length 

 of a horizontal line drawn from the posterior margin of ;the ocular 

 emargination to the cervical groove. The chela of the female is com- 

 paratively shorter and broader than in the male. Thus in the former 

 the greatest width of the palma usually equals half the lenght of the 

 whole chelae with the fingers, and sometimes exceeds that^ measure- 

 ment. In the male the chelae are larger and the fingers longer so that 

 the width of the palma never reaches half of the total length. I will 

 mention however that one of the females which I have examined has 

 rather masculine looking chelae. I think though that this can easily 

 be explained by assuming that these have been reproduced so recently 

 that they have not yet attained their full size and normal shape 2. 

 (Schluß folgt.) 



- They have also been pinched in some fight when their shell was soft so 

 ■that they show wounds which have not yet healed. 



