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1903.] PHILLIPS—A REVIEW OF PARTHENOGENESIS. 805 
on artificial parthenogenesis, but these must not be considered as 
arguing for a true natural parthenogenesis. 
Among Reptiles, Strahl (1892) reports irregular parthenogenetic 
cleavages. 
In the Birds, the evidence for a parthenogenetic development is 
perhaps the strongest of that for any vertebrates. It frequently 
happens that a blastoderm is formed on an egg which is appa-. 
rently not fertilized. Cases of this kind are found in the Chick 
(Coste, 1859; Oellacher, 1869 ; Koelliker, 1879, and others), in 
the Turtle Dove (Motta Maja, 1877; cited by Duval, 1884), and 
for several other birds (Duval, 1884). Balfour (1880) pointed out 
that care must be exercised in passing judgment on these cases, 
since it is known that spermatozoa can live for a considerable time 
in the female and that possibly these are really cases of fertilized 
eggs. ‘This is entirely upheld by the later work of Lau (1895) and 
Barfurth (1895), who show that eggs from virgin hens do not show 
cleavage in thé same way as do those from hens which have copu- 
lated with a cock even a considerable time before. In eggs from 
virgin hens the blastomeres do not have a cellular character, since 
all but a few lack nuclei, and when nuclei are present they do not 
divide mitotically. The blastoderm lacks all power of assimilation, 
the blastomeres are irregular and the whole shows no thickening at 
the posteriorend. There is never a segmentation cavity. Lauand 
Barfurth looked on such cases as due to a physico-chemical process, 
caused partly by evaporation and partly by coagulation of the pro- 
toplasm. Cases in which the female has previously copulated would 
then appear to be similar to those of the frog, in which there is a 
fertilization accomplished by a partially devitalized male cell. 
Even in Mammals, cases are recorded of the cleavage of the egg 
while still in the Graffian follicle. Janosik (1896) reports several 
cases (Rabbit) in which a cleavage has taken place, asemblance of a 
cleavage cavity formed and the whole mass has broken away from 
the membrana pellucida as in normal development ; but the phe- 
nomenon is so evidently connected with disintegration from the very 
beginning that it must not be considered as parthenogenesis. 
The question as to whether Dermoid cysts are due to the par- 
thenogenetic development of an egg has received a great deal of 
attention, and the exceptional case reported by Répin (cited by 
Duval, 1895) would point strongly to such an explanation as the 
true one. This cyst had four limbs and terminated in a kind of 
