164 THE INDUCTIONS OP BIOLOGY. 



is shown where the units or cells, as fast as they are seve- 

 rally formed, part company and lead independent lives. 

 This, in the vegetal kingdom, habitually occurs among the 

 Protopliyta, and in the animal kingdom, among the Proto- 

 zoa. 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 

 Thallophytes very generally exemplify this mode of de- 

 velopment. 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 Algce the Nostocs 

 and various other forms similarly show us an unsymmetrical 

 structure. Of Fungi we may say that creeping kinds display 

 no further dependence of one part on another than is implied 

 by their cohesion. And even in such better-organized plants 

 as the Marchantia, the general arrangement shows no refer- 

 ence to a directive centre. Among animals many of the 

 Sponges in their adult forms may be cited as devoid of that 

 co-ordination implied by symmetry: the units composing 

 them, though they have some subordination to local centres, 

 have no subordination to a general centre. To dis- 

 tinguish that kind of development in which the whole product 

 of a germ coheres in one mass, from that kind of develop- 

 ment in which it does not, Professor Huxley has introduced 

 the words " continuous " and " discontinuous; " and these 

 seem the best fitted for the purpose. Multicentral develop- 

 ment, then, is divisible into continuous and discontinuous. 



From central development we pass insensibly to that higher 

 kind of development for which axial seems the most appro- 

 priate name. A tendency towards this is vaguely manifested 

 almost everywhere. The great majority even of Protopliyta 

 and Protozoa have different longitudinal and transverse di- 

 mensions have an obscure if not a distinct axial structure. 

 The originally spheroidal and polyhedral units out of which 

 higher organisms are mainly built, usually pass into shapes 



