Philosophical Conceptions of Life. 253 
of its mass, so that it grows by a process of intussusception 
wholly unlike anything that occurs in the inorganic world. 
In the case of animal protoplasm, the mode of growth by 
intussusception is the same, but the capability of combining 
together mere inorganic elements into its own substance is 
lost; and, besides these, a certain amount of pre-existing 
vegetable or animal protoplasm must be present in the food, 
or growth will not go on. 
In both cases, when the growth has proceeded to a certain 
extent—within certain definite limits—a new characteristic 
phenomenon occurs in a growing mass of vegetable or animal 
protoplasm ; it multiplies by division, its whole mass partici- 
pating in the act, in accordance with one or other of a few 
definite methods. This process is repeated again and again. 
The progeny may separate, without modification, as inde- 
pendent forms, or, as in the case of the more complex organ- 
isms, they may cohere together, and the process culminates 
by groups of them undergoing certain definite and peculiar 
transformations, after which further multiplication becomes 
rare or ceases altogether, and the growth of the complex 
organism is thus limited. 
I cannot, of course, attempt this evening to describe all the 
known details of the progress of growth which I have thus 
hastily sketched; to give you a really satisfactory account of 
them would require a series of lectures. But I do not hesitate 
to say that the more fully you know these details the more 
unscientific you will think the attempt to class them as in any 
way similar to the circumstance that inorganic crystalline com- 
pounds seem “ each to havea size that is not usually exceeded 
without a tendency arising to form new crystals, rather than 
to increase the old.” It is, at the best, a waste of words to 
attempt to explain complex phenomena by comparing them to 
simpler ones which are fundamentally unlike them. 
I have but now referred to a process by which, in the growth 
of the more complex living beings, the small primitive proto- 
plasmic mass, out of which each individual arises, subdivides 
and produces a numerous brood of protoplasmic masses, at first 
closely resembling the parent mass, but after a time differing 
from it more and more, and finally undergoing transforma- 
tions into definite and peculiar forms. ‘This process, which 
does not take place in any disorderly manner, but in a very 
characteristic and definite way in each individual form, is 
designated by the term development. In point of fact, so 
far as it consists in the mere growth and multiplication of 
the individual elements that compose the organism, and the 
- imerease in size of the organism itself on account of these 
