THE THRESHOLD OF EVOLUTION. 
149 
a separation of the constituent atoms of any perfectly homo- 
geneous substance into two or more parts, cannot possibly take 
place otherwise than through some molecular or chemical 
change in their original constitution, such substance can no 
longer be said to be so homogeneous that every individual 
particle is an exact counterpart of every other particle of the 
mass. The entire definition and character based upon it is 
therefore demolished, and with it the foundations upon which 
the Haeckelian hypothesis of the Monera has been made to 
rest. 
Now in the early stage of every true Amoeba without ex- 
ception, granular particles, which undoubtedly constitute an 
integral portion of the organism even at this period, may be 
discovered scattered through its substance and taking part in 
the movements of the protoplasm, arising not from any circu- 
latory faculty resident within it, but from the changes of form 
undergone by the animal in throwing out pseudopodia for the 
purpose of creeping or rolling itself along the surface upon 
which it happens,’ for the time being, to be moving. This is 
rendered perfectly certain by the circumstance that when the 
body ceases to move, the ^^‘-circulation ceases also. In the 
free-floating Rhizopods, as, for example, the Foraminifera , Foly- 
cystina, Acanthometrce, and Dictyochidce , the same thing may be 
observed, though much less frequently, because in order to 
bring every portion of the body-substance in turn under the 
influence of the medium in which the organism lives, a very 
minute portion being exposed at a time beyond the shell or 
membranous covering, the vital contractility of the protoplasm 
is almost continually forcing some of the body-substance out of 
the foramina, and retracting within the shell a corresponding 
quantity. But wdiere a separation of the protoplasm has taken 
place into a clear portion nearly devoid of granules, or, as some- 
times is the case, more highly charged with them, it is always 
possible by dint of a little trouble to perceive that the central 
mass retains its character unchanged, there being, apparently, 
no longer a continuous interchange of protoplasmic substance 
between the central or nuclear portion and that which surrounds 
it. In the whole of the Rhizopoda the minute granules un- 
doubtedly go to form the true nucleus when this organ is 
fully developed, and in the lowest* order, in which no definite 
j single nucleus is present, to form the smaller reproductive 
organs, to which I gave the name of Sarcoblasts, as being 
the bodies from which the young of the species are developed, 
both Nuclei and Sarcoblasts are almost entirely made up of the 
granules, which are, however, too minute to admit of their 
structure being resolved. But if the still more minute granules 
seen by Messrs. Dallinger and Drysdale proved to be the germs 
