314 Proceedings of the Koyal Society of Edinburgh. [Sess. 
not, however, agree in form with that of the male of D. pulex, but more 
nearly approaches that of males of the genus Ceriodaphnia, e.g. C. ajjinis 
Lilljeborg.* 
When the foregoing account had been completed, I received from 
Dr W. E. Agar, of the University of Glasgow, the heads of two aberrant 
specimens of Baphnia pulex , which, together with some notes and serial 
sections of the trunks, he has kindly placed at my disposal. 
III. The first of these specimens was one of a brood of fifteen females, 
the other fourteen of which were normal, examined in May 1910. The 
right antennule (fig. 8) of this individual approaches in form that of a 
male. Its basal joint is exactly the same length as in the male, but is 
Fig. 8. — The aberrant riglit antennule of specimen III., right aspect. The outlines 
of the rostrum and of the left normal antennule, as seen on focussing 
through the right antennule, are indicated by dotted lines, x 300. 
F., flagellum; O.F., olfactory filaments; S . , seta. 
considerably stouter in its proximal and middle portions, narrowing, however, 
distally until its diameter is equal to that of the base of the flagellum. 
The olfactory filaments are of the usual form and number, but the flagellum 
is considerably larger than that of a normal male. The basal joint of this 
antennule bears a single seta, similar in form to, but larger than, that present 
on the antennule of a normal male. The rostrum of this specimen is much 
smaller than is usual in females, but the remaining characters of the speci- 
men are those of a normal female. Before this Daphnia was preserved it 
produced two broods, which together comprised thirty specimens, all normal 
females. Dr Agar kept these young individuals until they became mature 
and produced broods, altogether 281 specimens, of which 275 were normal 
females and 6 normal males. 
* Lilljeborg, W., “ Cladocera Suecise,” Nova Acta R. Soc. Sci. Ujpsala, Ser. 3, vol. xix. 
(1900). See pi. xxviii. figs. 25, 26. 
