PHYLLOPOD CRUSTACEA OP JAPAN. 153 



Museum, Uyeno Park, Tokyo, in the month of June, 1891. There 

 were then only parthenogenetic females, many of them cavrying more 

 than 30 eggs in their breeding chambers. Daring the course of 

 Summer and Autumn they produced two or three gamogenetic genera- 

 tions till at the end of November they completely disappeared. At the 

 end of March next year (1892), I again observed them in the same tank 

 but owing to the appearance of a species of Cypris the colony seemed 

 soon after to have entirely disappeared ; but they again came to 

 existance at the end of March 1893, and at the end of April of that year 

 the gamogenetic generations begun to appear, many of the females 

 which carry parthenogenetic eggs or embryos, in their breeding cham- 

 bers, producing gamogenetic eggs in the ovaries. At the beginning of 

 May, when I again observed them, they were almost all gamogenetic 

 females and males, and only a very few specimens of parthenogenetic 

 females were present among them. My experiments on the cyclic 

 generations of this species is not as yet quite completed, but from what 

 has been so far observed, it is certain that the present species is a 

 " palycyclic form " lilce its European allies. * 



The same species was also kindly sent to me by Mr. T. Sakai who 

 collected them in a small pond of standing water in the neighbourhood 

 of Soma on the 3rd of April, 1893. Among hundreds of specimens, 

 nearly six-tenths were parthenogenetic females, three-tenths gamo- 

 genetic females, and one-tenth or less males ; they were thus just 

 passing to the gamogenetic generation. 



Explanation of the Plate. 



Daphnia Whitmani, n. sp. 



Pig. I. Side view of a large sized female with about thirty partheuogonetic eggs iu 

 its breeding chamber. Zeiss' objective B, eye-piece 1. 



* See August Weisma.nn :— Dip Entstehung der cyclischen Fortpflanzung bei den 

 Daphnoideu ; Abhandlung VII. of the " Beitrilge zun Xaturgeschichte der Da.phnoiden." 

 Wilhelm Engelma.un, Leipzig, 187G-79. 



