On Fresh-water Entoniostraca. 23 



the microscope, that some of the zoosperms are poured out 

 from the genital openings, and in such cases I have always 

 found them to be simple, rounded, cellular bodies (fig. 11), 

 never showing any approach to the peculiar vermiform 

 shape described by Prof. Weismann in the male of M. 

 paradoxa. 



In living specimens of both sexes, the body is very 

 pellucid, and in the male almost colourless. In the female, 

 it generally exhibits a more or less distinct orange tinge, 

 and this would seem to be invariably the case with 

 individuals of the earlier generations, whereas those of later 

 generations, as a rule, become more pale in colour. 



The «summer-eggs» are at first, when received in the 

 matrix, very small and nearly colourless, with only a very 

 small quantity of nutritive yolk. They, however, rapidly 

 increase in size during the development, imbibing, as first 

 stated by Prof. Leydig, a nourishing fluid contained in the 

 cavity of the matrix, and secreted from a dense cellular 

 layer on the back of the parent animal. The «winter-eggs» 

 are considerably larger, and of a brick-red colour. 



Observations. — Of the present form, numerous speci- 

 mens developed in my aquaria, and in some of them multi- 

 plied in quite an astonishing manner, so as at last to fill 

 up the aquaria with myriads of individuals. The earlier 

 generations consisted exclusively of female specimens; but 

 after the lapse of some time, the characteristic ephippial 

 formation was beginning, and at that time male specimens 

 made their appearance in rather large numbers. After the 

 ephippia were deposited, some of the females again became 

 laden with summer- eggs, though generally not in such 

 great numbers as in the individuals of the earlier gener- 

 ations. From that time, the males gradually diminished in 



