190 J. LIONEL TAVLER [SEPTEMBER 
The fact that the male cell is in some cases attracted to the female by 
chemical products’ is some confirmation of this view. Conjugation 
would thus be allied to the phenomena associated with assimilation. 
So far, therefore, the evidence appears to be in favour of proto- 
plasm not being at any period directly influenced by climatic 
conditions. Protoplasm everywhere exhibits a tendency to select its 
food from its environment, and when it is unable to obtain such food, 
or is subject to conditions of environment which are unsuitable, it 
appears not to be rapidly modified, but is apparently eliminated. 
Protoplasm manifests in its different forms considerable resemblance 
to the more complex non-living chemical products, and this, so far as 
the inference is justifiable, points to the conclusion that certain 
conditions are essential for its development, that different forms of 
protoplasin require different conditions of environment, and that when 
any organism is not in sufficient harmony with its surroundings it is 
unable to live and is therefore eliminated. The constancy of the 
differences of the early forms of hfe would seem also to lead to the 
conclusion that protoplasm is never, or at most with extreme difficulty, 
directly modified by external influences. Lastly, the facts associated 
with conjugation and sex differentiation are apparently only explain- 
able on a pure or nearly pure selectionist hypothesis. 
Turning to another aspect of the facts relating to life, we find 
that while very considerable specialisation may be developed in 
unicellular organisms, yet when these organisms multiply they do so 
with very little alteration of the mother plasm, reproduction consisting 
in the separation of a portion of this mother substance, this portion, 
whether small or large, becoming a separate organism. 
In multicellular organisms, on the other hand, we see, besides this 
method of reproduction, another kind, which very early in biological 
evolution takes precedence over the more primitive method. The 
younger organism is developed from a structure that is not represented 
in the adult form, and the younger organism begins to closely resemble 
the older only after a period of development. In what respect is this 
latter kind of reproduction superior to the former? In the hydra 
we have an organism in which these two types co-exist. A new 
organism is sometimes developed as a simple out-growth of the 
mother substance, develops a mouth and tentacles, and with this new 
mode of obtaining nutriment gradually loses its connection with the 
parent organism and becomes independent. In other eases we find 
interstitial cells collecting into groups at different parts of the organism, 
in some of these groups the imner cells becoming slightly altered in 
shape, and developing thin, ribbon-shaped pieces of protoplasm or tails, 
by the aid of which they become capable of considerable powers of 
movement, and thus provided escape from the hydra into its surround- 
ing medium. Other groups of cells undergo a different change, one 
1 Hertwie’s work on ‘‘ The Cell” gives a brief résumé of some of these cases. 
