92 THE BEGINNINGS OF LIFE. 



the parent mass — that is to say, fission or gemmation 

 takes place. Nothing similar occurs in the crystal, 

 because this is a statical aggregate in which no mole- 

 cular rearrangements habitually occur. The tendency 

 which the molecules display to grow into a given form 

 is, however, not much more manifest in the crystal 

 than it is in the organism. The fundamental difference 

 between the two lies in the fact that the one is a 

 statical and the other a dynamical aggregate. As a result 

 of this difference, we find that the growth of the one is 

 always continuous, whilst that of the other is frequently 

 discontinuous — a ^ spontaneous ' separation of a portion 

 of its substance may, and frequently does, take place 

 in the case of the growing organism whereby self- 

 reproduction is brought about ^. 



^ Referring to the products of the multiplication of a single germ, 

 Mr, Herbert Spencer points out that ' total insubordination among the 

 centres of development is shown where the units or cells, as fast as they 

 are severally formed, part company and lead independent lives. This, in 

 the vegetable kingdom, habitually occurs among the Protophyta ; and in 

 the animal kingdom, among the Protozoa. Partial insubordination is 

 seen in those somewhat advanced organisms that consist of units which, 

 though they have not separated, have so little mutual dependence that 

 the aggregate they form is irregular. Among plants, the Thallogens 

 very generally exemplify this mode of development. Lichens, spreading 

 with flat or corrugated edges in this or that direction, as the conditions 

 determine, have no manifest co-ordination of parts. In the Alga, the 

 Nostocs similarly show us an unsymmetrical structure. Of Ftmgi, the 

 sessile and creeping kinds display no further dependence of one part on 



another than is implied by their cohesion To distinguish that kind 



of development in which the whole product of a germ coheres in one 

 mass from that kind of development in which it does not. Professor 

 Huxley has introduced the words "continuous" and "discontinuous;" 



