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OR ESSW EL 1 1 SH E ARE R . 
lisation is prevented seems to effectively prove their spermatic 
origin. 
With regard to maturation divisions, I am forced to admit 
that their evidence is very puzzling, and I am quite unable 
to explain them at present. In the case of the male egg, we 
should expect, as this has not been fertilised, and is therefore 
in a sense developing parthenogenetically, it should agree 
with the development of the male parthenogenetic egg of 
Rotifers and other forms, where they develop in the n con- 
dition, where n represents the reduced number of chromosomes. 
This is certainly not the case in Dinophilus, where the male 
egg, after reduction (if any reduction takes place), possesses 
apparently the full 2n number. It is, however, possible that 
the male egg of Dinophilus is similar to that of Phyl- 
loxerans, which develops in the 2n — 1 or — 2 condition, 
as it is so difficult to accurately count the chromosomes in 
the segmentation divisions of the male egg on account of 
their small size. In the female eggs we should expect 
them, since they have been fertilised before reduction, to be 
in the 2n + n condition, if we consider the sperm to bring in 
the n number. In the first maturation division of this egg 
we should find at least thirty chromosomes, whereas their 
number is somewhere about twenty. On the other hand, if 
we suppose the female germ-cells to be in the n condition 
when they appear in the ovary, then after fertilisation they 
should show the 2n number of chromosomes, which agrees 
with the facts, but does not explain how the male egg, which 
has not been fertilised, is nevertheless in the 2n — 1 or — 2 
Condition. Therefore, from whichever point of view we 
choose to regard it, there is no way of bringing the facts of 
the maturation divisions into line at present. 
The following is a summary of my conclusions : 
(1) In D. gyrociliatus the females are fertilised inside 
the egg-capsules by the males. 
(2) When the female germ-cells arise in the ovary they 
early enter into relation with the sperm, so that the nucleqs 
