T. H. Huxley on the Philosophy of Gemmation. 209 
some another, why some remain attached and some become de- 
tached, we know not. Such phenomena are for the present the 
ultimate facts of biological science; and we cannot understand 
the simplest among them, it would scem useless, as yet, to seek 
for an explanation of the more complex. 
evertheless, an explanation of agamogenesis in the Aphis 
and in like cases has been offered. It has been supposed to 
depend upon “the retention unchanged of some part of the 
primitive germ-mass ;’ this germ-mass being imagined to be the 
seat of a peculiar force, by virtue of which it gives rise to inde- 
pendent organisms. 
ine that the terminal chamber of the pseudovarium is full of 
nothing but “ unaltered germ-cells;” how does this explain the 
Phenomena? Structures having quite as great a claim to the 
title of “ unaltered germ-cells” lie in the extremities of the acini 
of the secreting glands, in the sub-epidermal tissues and else- 
Where ; why do not they give rise to young? Cells, less chang- 
leinctes of Aphis, and more directly 
om the primitive germ-mass, underlie the epidermis of 
On the whole, it would seem better, when 
