1903.] PHILLIPS—-A REVIEW OF PARTHENOGENESIS. 307 
parthenogenesis differ from what is normally found only in the 
greater proportion of parthenogenetic eggs. 
THE MATURATION OF PARTHENOGENETIC EGGS. 
The main point of interest in parthenogenesis is perhaps that of 
the maturation of the parthenogenetic eggs, cn account of its gen- 
eral bearing on the theory of fertilization and on account of its 
support of the theory of the individuality of chromosomes. 
Minot (1877), in an article on the theoretical meaning of matu- - 
ration, suggests that parthenogenesis may be due to failure to form 
polar bodies, and since the entire mass of chromatin remained in 
the egg it would be hermaphrodite and capable of development 
without the addition of any chromatin from the male cell. Balfour 
(1880) follows out the same line of thought in suggesting that the 
function of forming polar bodies has been acquired by most ova 
to prevent parthenogenesis, and van Beneden (1883) held a nearly 
similar view. 
Weismann (1886) found that one polar body is given off in the 
case of Polyphemus (Daphnid), and he later determined the same 
thing for parthenogenetic Ostracodes and Rotifers.* Blochmann 
(1888) found in Aphids that one polar body is given off in the case 
of eggs which develop parthenogenetically, while two are produced 
in eggs which require fertilization. Weismann was thus led to the 
view that the second polar body is of special significance in par- 
thenogenesis. In insects (Blochmann and others) the polar bodies 
are not thrown out of the egg as in most other animals, but the 
chromatin masses remain embedded in a vesicle in the proto- 
plasm of the egg, near the periphery, and are called ‘polar 
nuclei.’’ 
Boveri (1887) found in Ascaris megalocephala that the second 
polar body might remain in the egg (as is normally the case in 
insects) and give rise to a nucleus indistinguishable from the pro- 
nuclei. He, therefore, suggested that parthenogenesis might be 
due to the retention of the second polar body in the egg and its 
use as a male pro-nucleus.? ‘‘The second polar body would thus, in 
a certain sense, assume the rdéle of the spermatozoon, and it might 
1 Compare Lenssen (1899), Erlanger u. Lauterborn (1897) and Mrazek 
(1897). 
2 Boveri (1887), p. 73. 
