7i6 THE POPULAR SCIENCE MONTHLY. 



urae depends also on the organization, which enables the living thing 

 to assimilate substances in large quantity and to dispose of an amount 

 of nutrition in excess of the expenditure, just as a large capital, while 

 it gives the means of undertaking great enterprises, at the same time 

 yields increased profits. 



The integration by an organism of substances homologous with its 

 own has for its effect a segregation which increases the difference 

 between the organism and the environment, and at the same time 

 makes this difference stable. While the organism is being integrated, 

 at the expense of the environment, by deriving from it special mate- 

 rials, each organ is being integrated at the expense of the organism, 

 from which it derives, as from an environment, its special materials. 

 Like the organism, each organ diverges more and more, by a gradual 

 segregation, from the organs around about it. The organic units 

 which constitute it attract other units with the same polarity, diffused 

 throughout the fluids. This is not always the case, and homologous 

 units do not always exist ready made in the nutrient fluid. More 

 generally the organic units find in the fluids only the elements neces- 

 sary for the production of homologous units, and segregation is per- 

 fected by a phenomenon of the nature of a genesis. Still in this case, 

 as in the preceding, the result is a more perfect differentiation of the 

 parts of the organism, an increase of heterogeneity, and augmentation 

 of the distinction between the different parts, and ultimately the for- 

 mation of a structure and of an actual organism. This result is called 

 development. 



Expressed in general terms, development is the transition from a 

 state of incoherent homogeneity to a state of coherent and definite 

 heterogeneity ; from a state wherein the parts are all alike, or rather, 

 where there are no distinct parts, to a state wherein there are parts 

 clearly defined, with fixed forms and attributes. The bud of a plant 

 consists of a hemispherical or subconical projection which, at its apex 

 especially, is made up of a transparent mass of cells not yet organ- 

 ized into tissues. This mass grows owing to the rapid multiplication 

 of the cells, lengthens, sends forth other similar projections having a 

 like homogeneous structure; from this come leaves. As the branch 

 develops, the cells, which at first were identical, assume different 

 characters, till at last they lose all resemblance to one another. The 

 same thing takes place in man. His arm is at first simply a little bud- 

 ding prominence on one side of the embryo, consisting of simple cells 

 without any signs of arrangement. Soon there appear vessels, and 

 later the cartilaginous parts from which are produced the bones, the 

 gelatin-like bands which afterward are transformed into muscles, etc. 

 In the individual we see the first phase of existence characterized by a 

 state of homogeneity wherein nothing is distinct, and we follow step 

 by step the gradations of its transition to a greater complexity, and to 

 states characterized by increasing distinction of parts, as their dissim- 



