58 ON THE AGAMIC REPRODUCTION AND MORPHOLOGY OF APHIS 
ment in the form of a bud, which becomes the seat of the subsequent 
processes of growth and development; a clear cavity or centre of 
assimilation is first formed, which soon opens into the stomach of the 
parent; but the communication is afterwards closed, and the young 
hydra is ultimately cast off from the surface of the parent.” 1— 
“Lectures, 2nd ed., p. 124. 
I have had occasion carefully to watch the process of gemmation 
not only in Hydra, but in many species of all the other subdivisions 
of the Hydrozsoa ; and I venture to assert that no such process as that 
described by Professor Owen takes place in any one of them. 
The bud is from the first in communication with the cavity of the 
body, of which it is a mere diverticulum, whose walls are a little 
thickened at the extremity. No special cell or group of cells can be 
discovered as the centres whence growth proceeds.. No “integu- 
ment” is pushed out by any thing beneath it; but the outer layer 
of the body of the animal thickens and grows par? passu with the 
growth of the bud. No especial accumulation of derivative germ- 
cells can be seen in any part of the body of any Aydrozoon ; and 
before gemmation commences there is no distinguishable difference 
of texture between the part in which gemmation commences and any 
other portion of the body. Furthermore, if a complex Hydrozoon, 
such as a Physophora or Agalma, be examined, it will be found that 
there is no histological distinction whatsoever between that part of 
the body which is to give rise to a free swimming generative zooid, 
and that which produces merely a bract, a tentacle, or a stomach. 
In this case, then, as in that of the pfs, the hypothesis receives 
no support from, but is totally opposed by, facts ; and I unreservedly 
adopt the conclusion (long since clearly and well expressed by Dr. 
Carpenter), that “spermatic force” is but a name without definite 
meaning, applied to that which is not proven to exist, and the 
assumption of whose existence, even, does not help us a single step 
towards the understanding of the wonderful phenonema of agamo- 
genesis. 
Truly we may say, with Degeer (4.4 p. 129), “Les Pucerons sont 
des insectes bien capables de déranger tout systéme formé de généra- 
tion, et de mettre en déroute tous ceux qui s’efforcent d’expliquer ce 
mystere de la nature.” 
But the question may be asked: if the “spermatic force” be a 
myth, what zs the cause of the phenomena? Considering that the 
groundwork of modern physiology is not a score of years old, I do 
' T have cited this passage from the ‘ Lectures’ rather than from the work on * Partheno- 
genesis,” as they may be supposed to contain the expression of the author’s latest views. 
