ON THE MOLECCLAR ORIGIN OF INFUSORIA. 
61 
or growth from their extremities. It may frequently be seen 
that No. 3 is composed of molecules of exactly the same size as 
No. 2, which are floating loose — a fact in favour of their coale- 
scence rather than of their division, as then they would be re- 
duced to half the size. It is more probable that although the 
smaller molecules may increase by imbibition of fluids, they 
have yet a constant tendency to aggregate together and melt into 
one another. No. 3 is not a proof of No. 2 dividing, but of two 
molecules coalescing; and when they unite, they form No. 4. 
Two or more of these uniting, form Nos. 5 and 6. When a 
similar process to this goes on in mineral bodies, as shown by 
Mr. Eainey, * it cannot suggest division, but union ; and this for 
the obvious reason, that the former would lead to disintegration, 
whereas, it can be seen in one case as in the other, that develop- 
ment is the result. In short, in the same manner as a tube is 
formed by a coalescence of cells, so is this minute vibratile 
vibrio formed by the coalescence of molecules. It may be 
argued, however, that each molecule elongates itself — that is. 
No. 2 is converted into No. 4; this into Nos. 5 and 6 ; and that 
No. 3 are sporules or ova, caused by the disintegration of No. 6. 
But this view is opposed by the fact that Nos. 1, 2, and 3 are 
seen before Nos. 4, 5, and 6 are produced. Of this all have 
satisfied themselves who have examined animal and vegetable 
infusions ; and the conclusion, therefore, cannot be resisted, 
that the vibrios are derived from the molecules, and not the 
molecules from the vibrios. 
But it may also be supposed, that while some have the pro- 
perty of dividing, others are capable of elongating or aggregat- 
ing ; but this view is not only opposed to observation, but is at 
variance with all that we know of embryonic development in 
plants and animals. When a plant consists of a single structural 
element, such as a cell or a tube, it will, I think, be admitted 
that growth in the sense of increased bulk, and growth in the 
sense of multiplication of parts by division, do not proceed at 
the same moment of time. Every plant and animal follows, in 
this respect, the same law. Nutrition is carried on up to a cer- 
taTn point of maturity, and then, and not till then, does gener- 
ation, or the separation of parts to form new creatures, take 
place. When plants and animals are complex in their structure, 
one organ or segment may be growing, while another is disin- 
tegrating; but in individual organs there is a period for growth 
and reparation, and a period for division or separation. Hence, 
it seems to me, I am correct in thinking that if the piimary 
molecules on the surface of an infusion possess the property of 
dividing, they cannot also, at the same moment, possess the 
* On the Mode of Formation of Shells/’ &c., p. 12. 8vo. London 
1855. 
