1912-13.] Pseudo-hermaphrodite Examples of Daphnia pulex. 307 
XXVII. — On some Pseudo-hermaphrodite Examples of Daphnia pul ex. 
By J. H. Ashworth, D.Sc., Lecturer in Invertebrate Zoology in the 
University of Edinburgh. 
(MS. received July 7, 1913. Read July 7, 1913.) 
Among about a hundred specimens of Daphnia pulex (De Geer) obtained 
for class purposes, at the end of May, 1912, I found two females* in each 
of which the antennule of one side resembled that of a male. These cases 
seem worthy of notice in view of the paucity of existing records of similar 
abnormalities in Daphnia. 
Previous Records of Abnormalities of the Antennules in Cladocera. 
Kurz*|- found, in October, 1873, an example of D. pulex in which the 
right antennule was short, as in the female, while the left approached in 
form that of the male, though it was not quite as large as the latter. The 
first trunk-limb on the right side was like that of the female, while the 
left one possessed a prehensile hook and flagellum, as in the male. The 
right gonad was an ovary, the left a testis. The head, carapace, and 
abdomen more nearly resembled those of a female, except that the anterior 
margin of the carapace was not evenly rounded but humped — not, however, 
as strongly as in the male, — and fringed with long hairs. Early in August, 
1873, Kurz observed a specimen of D. schaefferi Baird (a variety of 
D. magna Straus), which presented a right antennule like that of the 
female ; but the left, though similar in form to that of the male, was con- 
siderably less than the latter, and lacked the seta present on the anterior 
margin of the antennule in males. The trunk-limbs, the abdomen, and the 
carapace were of the female type. The reproductive organs of this specimen 
were not examined. 
The third abnormal Cladoceran recorded by Kurz was an example of 
Alona quadrangularis (0. F. Muller), taken on November 1, 1873, which 
had the general appearance of a male. The right and left antennules were 
equally long (as long as the rostrum) and provided with olfactory filaments, 
but the left one bore also a flagellum, like that of the male. The right first 
trunk-limb was of the form usual in the female; the left one was hook-like 
* The entire collection was carefully examined ; males were not present. 
t “Uber androgyne Missbildung bei Cladoceren,” Sitzb. K. Akad. Wiss. Wien, Math.- 
natunv. Klasse , Bd. lxix., i Abt. (1874), pp. 40-46. 
