1885.] 
Fecundation of Animals, 
25 
chromatic loops. These four chromatic loops take part in 
the formation of the chromatic star, but they remain 
distinct. Each of them becomes divided longitudinally in 
two secondary twin loops. 
The nuclei of both the first blastomeres receive each a 
half of each primary loop, or four secondary loops, of which 
two are male and two female. 
There occurs therefore no interfusion between the male 
and the female chromatine in any stage. If such a process 
takes place it can only be in the nuclei of the two primary 
blastomeres. There is reason for believing that even in 
these nuclei the male chromatine remains distinct from the 
female. It is certain that the male chromatine never 
unites with the female to form the primary embryonal 
nucleus. We cannot, therefore, maintain with Hertwig 
that fecundation consists in the union of two nuclei, a male 
and a female. No such union takes place in Ascaris. If it 
occurs in other living beings it is probably only in appear- 
ance, and it is certainly not the essential part of the pheno- 
menon. Fecundation is, in its essence, substitution, — i.e., the 
replacement of a part of the germinal vesicle by nuclear 
elements derived from the spermatozoon, and perhaps also 
of a part of the protoplasm of the ovum (perivitelline sub- 
stance) by the spermatic protoplasm. 
The elements of male and female origin do not coalesce 
to one segmentation-nucleus, and remain probably distinct 
in all the cells descended from them. 
The study of the maturation of the ovum, of fecundation, 
and of cell-division have confirmed me in the view that the 
cell-nuclei are hermaphroditic, and this the more as the 
male chromatine does not coalesce with the female chroma- 
tine. If the^male and the female pronucleus deserve their 
respective names, which pre-suppose their sexuality, the 
cell-nuclei are evidently hermaphroditic. The tissue-cells 
have this character in common with the Protozoa and the Proto- 
phytes. 
I consider fecundation not as generation. This charac- 
teristic phenomenon of cell-life consists in an exchange, and 
not in the genesis of a new cell-individual. The substitution 
of certain elements of a cell by similar parts, supplied by 
another cell, renders possible the unlimited preservation of 
life, and renders further increase possible. We can con- 
ceive of generation (reproduction) only as an increase of 
individuals. It is probable that in reality there exists 
only a single mode of increase-fission. In fecundation 
there is no increase in the number of individuals. This 
