1912-13.] Pseudo-hermaphrodite Examples of Daphnia pulex. 309 
inspected, and in all except one some abnormal examples were found. In 
some specimens the only abnormal feature was a slight enlargement of one 
or both antennules ; in others, one or both antennules were larger but still 
of the female form, and the first trunk-limbs were either normal ( i.e . as in 
the female) or exhibited a small hook ; in eleven other cases one or both 
antennules resembled those of the male, and in five of these the first trunk- 
limb of one or both sides possessed a hook. Accurate records were kept 
of the sixth to the twelfth broods, comprising altogether 104 specimens. 
Of these 79 were normal females, 1 a normal male, and 24 exhibited one 
or other of the abnormal features above mentioned. The third generation 
presented abnormalities ; among the 350 specimens comprising this genera- 
tion there were 253 normal females, 85 pseudo-hermaphrodite females, 
3 true hermaphrodites, 3 pseudo-hermaphrodite males, and 6 normal males. 
In the fourth generation, 17 pseudo-hermaphrodites occurred among 80 
individuals. Kuttner pointed out that the proportion of normal females 
.to specimens exhibiting male characters was nearly 3:1, and, while not 
interpreting this as an indication of the operation of inheritance on Men- 
delian lines, she remarked that the constant proportions indicated that the 
explanation of their occurrence was to be sought in the domain of 
“ Vererbungsmechanik,” but she concluded that the problem was of so 
complex a character that its solution was at present impossible. 
Description of Abnormal Specimens of Daphnia pulex. 
I. The first specimen now to be described is remarkable for the form 
of its left antennule. This appendage (figs. 1 and 2) is well developed, 
and has the general structure and proportions of the corresponding antennule 
of a normal male (fig. 4), and was probably movable. It bears on its 
slightly concave distal end seven olfactory filaments, and on its anterior 
margin, a little beyond the middle of its length, carries a single pointed 
seta, like that present in a corresponding position in the male. This 
antennule differs in one respect from that of a male, in that instead of 
having at its distal end a prehensile flagellum about T2 mm. in length, 
there is a seta only *024 mm. long. This seta is bulbous at its base, and 
its distal portion is short and finger-like, whereas the corresponding 
flagellum of the male has a long cylindrical basal portion and a tapering 
distal portion of about equal length. 
The right antennule of this specimen (fig. 3) agrees exactly in form 
and size with that of a female, and its olfactory filaments exhibit the 
usual arrangement and structure. 
