Heredity. 
215 
allowing it to evaporate while exposed to direct sunlight. One of 
these organisms, seen under the microscope, has the appearance of a 
particle of jelly, and usually is continually changing its shape ; hence 
has been given to it the name of the Proteus Animalcule, or 
Amoeba. One of the most striking phenomena associated with 
Amoeba is the manner in which it produces fresh Amoebae. The 
individual Amoeba is a single cell— it is an unicellular organism — 
and, by its simply dividing into two, a couple of Amoeba; come into 
existence where before there was only one. Neither of these new 
cells produced by the process of fission — as it is termeol — can be 
regarded as the parent of the other, and, in due course, each of the 
new Amoeba; will in turn undergo fission, and give rise to a still 
younger generation. It is possible, then, that in looking at an 
Amoeba we may be gazing upon something which has been continu- 
ously living from the time when life first appeared upon the globe, 
and the question, Is Amoeba immortal 1 is by no means chimerical. 
Weismann says : — 
"The process of fission in the Amoeba has recently been much discussed, 
and I am well aware that the life of the individual is generally believed to 
come tu an end with the division which gives rise to two new individuals, 
as if death and reproduction were the same thing. But this process cannot 
truly be called death. Where is the dead body ? What is it that dies ? 
Nothing dies ; the body of the animal only divides into two similar parts, 
possessing the same constitution. Each of these parts is exactly like its 
parent, lives in the same manner, and, finally, also divides into halves. As 
far as these organisms are concerned, death can only be spoken of in the 
most figurative sense." 
Not Amoeba alone, then, but the low, unicellular water-plants, 
and even highly-organised unicellular structures, such as the Infu- 
soria, never die. They may be destroyed by heat, poisons, ice., but 
they none the less carry in themselves the potentiality of unending life 
— " death which arises from internal causes is an impossibility among 
these lower organisms." 
Next are discussed the multicellular plants and animals — that 
is, all those organisms which consist of more than one cell. It is 
pointed out that the constituent cells came to be divided, in the in- 
dividual organism, into two groups— the somatic (Gr. soma, the body) 
and reproductive ; in other words, the cells of the body, as opposed 
to those which are concerned with reproduction. As the complexity 
of the body increased, the two groups of cells became more sharply 
separated from each other. 
" Very soon the somatic cells surpassed the reproductive in number, and 
during this increase they became more and more broken up, by the principle 
of the division of labour, into sharply-separated systems of tissues. As 
these changes took place, the power of reproducing large parts of the 
organism [e.g., the lobster its claw, the salamander its tail or foot, the snail 
its horns, &c] was lost, while the power of reproducing the whole individual 
became concentrated in the reproductive cells alone." 
Another step in the argument is based upon a consideration 
of the necessity for division of labour amongst the cells of an 
organism consisting at first of a colony of similar cells : — 
