444 
yolk mechanically. Others have formed the idea that the germinal 
vesicle bursts, and that its included granules constitute the germs of 
those cells which subsequently form in the germinal mass- Others, 
again, suppose that on impregnation the germinal vesicle divides 
first, and that the molecules of the yolk are attracted round the 
two centres so formed. But numerous observations had satisfied the 
author that both spermatozoid and germinal vesicles are simply 
dissolved among the molecules of the yolk, from the substance of 
which, stimulated and modified by the mixture so occasioned, the 
embryo is formed ; a view which has further the merit of explaining 
what is known of the qualities of both parents observable in the 
offspring. He was only acquainted with one exception to this general 
law, viz., the development of Pyrozoma , recently described by Mr 
Huxley, the description of which, however, was incomplete.* The 
truth appears to be, that in an analogous manner to that in which 
the pigment molecules of the skin are stimulated by the access of 
light to enter into certain vital combinations with one another, so 
are the molecules of the yolk stimulated by the access of the sperma- 
tozoid to produce those other vital combinations that result in a 
new being. The essential action is not so much connected, as has 
hitherto been supposed, with the cell wall or nucleus as with the 
molecular element of the ovum. 
With regard to nutrition — food and all assimilable material must 
be reduced, in the first instance, to the molecular form, while the 
fluid from which the blood is prepared, viz. chyle, is essentially 
molecular. Most of the secretions originate in the effusion of a 
fluid into the gland follicle, which becomes molecular, and gives 
rise to cell formation. In muscle, the power of contractility is in- 
herently associated with the ultimate molecules of which the fasciculus 
is composed; and lastly, the grey matter of the sensory ganglia, 
and of the brain, which furnishes the conditions necessary for the 
exercise of secretion, and of even intellect itself, is associated with 
layers of molecules which are unquestionably active in producing 
the various modifications of nervous force. These molecules are con- 
stant and permanent as an integral part of these tissues, as much as 
cells or fibres are essential parts of others, and their function is not 
transitory, but essential to the organs to which they belong. 
All these facts point to the conclusion that vital action, so far 
* Annals of Natural History, Jan. 1860, p. 35. 
