256 
only rational distinction which can be made between endo- 
genous cell-formation and cell-division consists in this, that 
in the multiplication by division the nuclei of the daughter 
cells form at the expense of the nuclei of the pre- existing 
cell; whilst in the multiplication by the endogenous method 
(which the botanists call “ free cell-formation 3) the nucleus 
of the daughter cell develops in the body of the mother cell 
without the participation of a pre-existing nucleus. 
Each of these two modes of multiplication can present 
itself in connection with a sort of budding. The multipli- 
cation by budding is only a particular case of the two funda- 
mental modes of cell-multiplication. What distinguishes 
this particular mode of division is, that in the case of budding, 
a generating and an engendered element can be distinguished, 
a mother cell and a daughter cell; whilst in division, pure 
and simple, the two cells are derived from one mother cell; 
they are, both one and the other, daughters, and therefore 
sister cells. 
It is undeniable that the formation of the nucleus in the 
body of the pseudo-filaria presents us with a true endogenous 
generation, following on a multiplication by budding ‘of the 
generating cytod. 
The only examples of endogenous generation which I 
have found mentioned are the endogenous formation of the 
blastodermic cells in the eggs of a great number of insects, 
especially of the Diptera;! the development of an entire 
layer of cells in the interior of the vitelline membrane of the 
ovarian egg of the Ascidia canina, without the germinal 
vesicle participating in the least degree in the formation of 
these cells;* and finally, the generally admitted fact of the 
formation of a nucleus in the egg of animals after fecunda- 
tion, to replace the germinal vesicle. 
The observations of Weissman on the formation of the 
blastodermic cells do not appear to me conclusive; they do 
not demonstrate that the nuclei which appear in the proto- 
plasmic layer (Keimhautblastem) are not derived from the 
germinal vesicle. It is notorious that the opacity of the 
vitellus of the egg of insects generally, renders these delicate 
observations impossible. And Weissmann’s interpretation 
is rendered doubtful by the fact that in the Cecidomyie and 
the Aphides, where the vitellus is nearly transparent, the 
nuclei of the blastodermic cells are derived from the germi- 
1 Weissmann, ‘ Entwickelung der Dipteren.’ 
> Kupffer, “Die Stammverwandtschaft zwischen Ascidien und Wirhel- 
higeen ‘Archiv fiir Mikr. Anat.,’ Bd. vi, 1870. 
