282 Evolution of Branchiopod Crustaceans. [April, 
this new species.’ The factor that produced the individual Z was a 
compelling mechanical cause originating in a pathological condi- 
tion. According to Dr, Darwin, the mechanical cause enters into 
activity with the appearance of “favorably varying ” individuals 
whose morphological deviations are either inherited or adapted. 
As to C, the genus Chirocephalus, I have reason to suspect in the 
lobed and prolonged frontal tentacles only a product caused by 
either chemico-physical or a sudden change in climatological 
influences. The successive appearance of Chirocephalus and 
Streptocephalus in one and the same pond near Woodbury, N. Y Big 
rather strengthens my assumption. 
The hermaphroditic form D shows characters closely relating 
it to set A. From the study of comparative anatomy it follows 
that hermaphroditism, 2 ¢, the coéxistence of both male and 
female sexual organs in one individual, is the primitive condition 
of sexual differentiation, which may in time be followed by a 
complete separation of the sexes. Hermaphroditism and _par- 
thenogenesis can be regarded as cases of atavism—as a reoccur- 
rence of former, primitive conditions. Further progress in differ- 
entiation of the sexual conditions, Haeckel ascribes to “ division 
of labor” (Arbeitstheilung). The bilateralism in this hermaphro- — 
dite indicates close relationship and codrdination between the 
sexual organs and auxilliary copulation organs. According to 
Dr. Chas. S. Minot’s theory,’ it is possible that a male genoblast 
was formed by the splitting of a neutral cell on one side, anda 
female genoblast in the same manner on the other side of the 
post-abdomen at an early larval stage, and that then, as the animal 
became gradually more developed, the second pair of antennz 
(not hitherto sexually distinguishable) transformed themselves 
symmetrically in accordance with the bilateral position of the 
genital glands and their exits. Unfortunately we are absolutely 
ignorant of the conditions which cause an animal, when capable 
of making genoblasts, to produce either male, female or her- 
maphrodite. 
1 Professor Huxley’s ** The Cr efiahi: Zs 1 a ay morphological sense, 4 
species is simply an assemblage of individuals which agree with one another and a : 
fer es the rest of the living world in the sum of their Sieklcgte characters.” 
A, Ryder, op citat 
3 It j is not impossible that branchiopod Crustaceans are liable to produce seasonal 
dimorphic individuals, a parallel to cases observed in Lepidoptera, according to Pro- 
fessor Sam. H. Scudder, Professor A. Weismann and others 
4 Professor Ernst Haeckel’s “ Anthropogenie,”’ pages 308, 681, etc. 
5 AMER. NAT., XIV, Feb., 1880, 
