I 12 



REPORT OF THE COMMISSIONERS OF 



Appliquecs, a writer who appeared to me to be exaggerating in other matters that 

 I knew something about, gave this estimate : 'that the descendants of a single female 

 Daphnia would in sixty days amount to 1,291,370,075 individuals.' That is 



astounding enough and I am not yet ready to accept it, but Mr. makes a female 



Daphnia do about four-fifths as much in twenty-four hours. 



"We have studied Daphnia some at this station, kept them in aquaria and under 

 such restraint as enabled us to follow their reproduction. The eggs are large, the 

 brood cavity could not hold a hundred of them at once, I should say that less than 

 fifty would be the average. In the summer they hatch in the brood cavity and 

 come out alive and kicking. It takes three or four days for eggs to mature and 

 come forth, and about a week for the young to come to maturity so as to reproduce. 

 Of course, I recognize the possibility of European Daphnia being more prolific 

 than ours. 



"At Wood's Holl there was an abundance of two species of Daphnia, one of them, 

 I think, Daphnia pulex, the other a very large one, say one-fifth or one-quarter of 

 an inch long, the largest I ever saw." 



Fig. 12. Daphnia "bearing- eggs. 



Mr. Atkins sent me specimens of two species of Daphnia, and one individual 

 bearing eggs was enlarged in a drawing for this paper, in the office of the State 

 Entomologist, and is shown in Fig. 12. About forty eggs can be counted in this 

 single specimen, which it will be noticed 'is of a different species from that shown 

 in Fig. 1 1. 



While preparing this paper I was suddenly confronted by a dilemma which was for 

 the moment most embarrassing. The drawings and plates of the figure had been 

 made of the Daphnia, and my notes commending the crustacean as fish food were 

 practically ready for the printer when incidentally Dr. Tarleton H. Bean, Director of 

 the New York Aquarium, informed me that in translating from the French a 



