SYNOPSIS 393 



VIII. UNICELLULAR AND DIPLOBLASTIC ANIMALS. 



PACK 



a. In plants there is a clear transition from unicellular forms to 

 solid aggregates, but in animals the connection of the 

 gastrula with unicellular forms is uncertain 264 



l>. Hypothesis of the origin of multicellular forms from a colony 



of unicellular zooids 265 



C. Other matters of general importance, such as the composition 

 and properties of protoplasm, cellulose, chlorophyll, starch, &c. : meta- 

 bolism : holozoic, holophytic, and saprophytic nutrition : intra- and 

 extra-cellular digestion : amoeboid, ciliary, and muscular movements : 

 the elementary physiology of muscle and nerve : parasitism and sym- 

 biosis : asexual and sexual generation : and the elements of embryology 

 are discussed under the various types, and will be most conveniently 

 referred to by consulting the Index. 



