i go /. LIONEL TAYLER [September 



The fact that the male cell is in some cases attracted to the female by 

 chemical products x 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 

 protoplasm 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 life 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 cases we find 

 interstitial cells collecting into groups at different parts of the organism, 

 in some of these groups the inner 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 Hertwisr's work on " The Cell " wives a brief resume of some of these cases. 



