76 
Druce, on Confervoidece. 
from an altered condition of two halves of a single frustule^ 
as in Melosira and Ortliosira^ and probably tbrougbout the 
filamentous group. The same process has been observed 
among certain of the Naviculse, in Acnanthes^ and other or- 
ganisms ; and it may, I think, be safely concluded that if con- 
jugation were the process which, in one shape or other, the 
student had to discover as the true generative act among the 
Confervoidese, its essential conditions would not vary ; and, 
moreover, considering that the majority of these organisms 
are admitted to be unicellular, and the conditions of a true 
generative act consist in the union of two cells of different 
characteristic endowments, although each cell may produce 
many by internal gemmation, it is difficult to conceive that 
the product of this vegetative multiplication can ever result 
in a sperm and germ cell from the same parent. The theory 
I would very diffidently offer to your notice is — that as a 
certain definite amount of germ capacity only is conferred by 
each generative act, the tendency of each growth by vegetative 
multiplication is towards the degeneration of the organism. 
This is evidently true and palpable to any one who has grown 
Confervse in an aquarium, where the nutritive elements are 
not so abundant as in their native waters. In order, there- 
fore, to prolong this power of multiplication, two cells com- 
bine to produce one, by the mere fusion of their respective 
cell-contents ; and in cases where two spores are formed, and, 
as we have seen not unfrequently in Spirogyra, after fusion 
the contents part again into two reproductive bodies. I 
would further venture to propose that the germ cells in these 
orders are very imperfectly differentiated, and that up to the 
period of fecundation there is no real difference between the 
preparation of the cell-contents for zoospores and real spores ; 
and that these unfecundated spores may become encysted, 
and are sporangia, while those fecundated are, in all cases, in 
due time developed in the likeness of their parents. A 
curious confirmation of this doctrine here occurs to me in the 
only instance of conjugation, so called, among a class of 
animals so high as the Articulata, — one of the Trematode 
Entozoa, Diplozoon paradoxum a parasite upon the gills of 
certain fishes, which in its young state, Diporpa, is destitute 
of the organs of leproduction, but at a certain stage of their 
existence two previously independent individuals are partially 
fused into each other, and become one bi-sexual organism. 
Here surely we may conclude that each of these Diporpse does 
not in itself possess sufficient germ capacity to become perfect, 
but that the united capacity of both affords the requisite 
accumulative power ; and here there can be no question as to 
