300 PHILLIPS—A REVIEW OF PARTHENOGENESIS.  [Oct. 16, — 
pletely acquired, since the female must here wait until she reaches 
the pupal stage before she is sexually matured, and then she has not — 
the power of viviparity but must lay her eggs; viviparous reproduc- 
tion being undoubtedly an advantage to a species from the stand- 
point of increasing their numbers. It would then seem that some 
Diptera have not only acquired the advantage of parthenogenetic 
development but have shifted this power back to the pupa, or even 
larva, so that they may still more profit by this specialized method 
of reproduction. 
ORTHOPTERA.—The development of eggs without fertilization has 
recently been described for this group by several] persons. Dom- 
inique (1899) obtained parthenogenetic development (thelytoky) in 
Bacillus gallicus, while Heymons got one male to every twenty to 
twenty-five females in the parthenogenetic offspring of B. Rossiz ; and 
Azam (1898) and Stadelman (1898) also got some parthenogenetic — 
individuals in the last-named species. Bolivar (1897 and ’99) got © 
three cases out of ten in which isolated larvee of Heptynia hespanica — 
produced eggs which developed ; but he is not sure that they were ~ 
not fertilized, although Pautel describes parthenogenesis as occurring 
in this species [cf. also Brunn (1898)]. ; 
From the evidence now at hand it would appear that partheno- 
genesis in this group is exceptional. 
CRUSTACEA. 
Next to plant lice, our earliest knowledge of the develop-— 
ment of unfertilized eggs was for cases among the Crustacea. 
Schaffer (1755) described the development of eggs from unfertilized 
females of Daphnids, and by isolation he succeeded in producing 
several generations without fertilization and described this as being 
similar to what was known to take place in Aphids. Ramdohr- 
(1805) raised ten successive generations parthenogenetically, and 
Jurine (1820) also confirmed the work. Ramdohr, however, did 
not look on these forms as true females but as hermaphrodites. 
These observations were on summer eggs, there being practically 
the same difference in this group as we find in Hemiptera. The 
summer eggs as in Aphids develop parthenogenetically, while the 
winter eggs require fertilization. 
v. Siebold (1856) stated that he thought that Aus cancriformis, 
Limnadia gigas and Polyphemus oculis, in which no males had been 
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