Certain types, which are transitional between _Protozoa_ and _Metazoa_, exhibit under its simplest form the relation between self-maintenance and race-maintenance--the integration primarily effecting the one and the disintegration primarily effecting the other. Among the _Mycetozoa_ a number of amoeba-like individuals aggregate into what is called a plasmodium; and while, in some orders, they become fused into a mass of protoplasm through which their nuclei are dispersed, in other orders (_Sorophora_) they retain their individualities and simply form a coherent aggregate. These last, presumably the earliest in order of evolution, remain united so long as the plasmodium, having a small power of locomotion, furthers the general nutrition; but when this is impeded by drought or cold, there arise spores. Each spore contains an amoeboid individual; and this, escaping when favourable conditions return, establishes by fission and by union with others like itself a new colony or plasmodium. Reduced to its lowest terms, we here see the antagonism between that growth of the coherent mass of units which accompanies its physical prosperity, and that incoherence and dispersion of the units which follows unfavourable conditions and arrest of growth, and which presently initiates new plasmodia. This antagonism, seen in these incipient _Metazoa_ which show us none of that organization characterizing the _Metazoa_ in general, is everywhere in more or less disguised forms exhibited by them--must necessarily be so if growth of the individual is a process of integration while formation of new individuals is a process of disintegration. And, primarily, it is an implication that whatever furthers the one impedes the other.