ORGANIC EVOLUTION — THE FACTORS 65 



the sarcode, by which the morphological value of the 

 ihizopod body as cell or cell-aggregate is placed 

 beyond all doubt. There are also forms in the 

 protoplasm of which no trace of a cell-nucleus has 

 been found. In such, either the protoplasm of the 

 nucleus is not differentiated as a separate structure 

 (the monera of E. Haeckel), or we have to do with a 

 transient non-nucleated stage in the life-history." If 

 the sponges be included in this class it is true that in 

 them there is a " syncytium or layer of structureless sar- 

 code;" but of it Dr. Nicholson says — "Others of the 

 sarcodes again become indistinguishably amalgamated 

 with one another in progress of gi'owth, and thus give 

 rise to a so-called ' syncytium ' or layer of structureless 

 sarcode." 



Whenever a structureless, or apparently structureless, 

 sarcode occurs among rhizopods, we may well believe 

 that it has arisen in them, as in their allies the sponges, 

 through the instrumentality of cells. In higher animals 

 I think Mr. Spencer is demonstrably wrong in suppos- 

 ing that any tissues arise independently of cells. 

 Fibrous tissue certainly results from cell-formation and 

 modification. Bone and cartilage are, it is true, not 

 entirely cellular, but in both the interstitial substance 

 between the cells, a product of their activities, is an 

 exaggerated and modified cell-envelope. Therefore, 

 since in animals higher than the rhizopods cells are 

 universal, and since in animals lower than the rhizo- 

 pods (the lower unicellular organisms) they are of 

 course also universal, it would be inexplicable if in the 

 intermediate animals, the rhizopods, which presumably 

 mark a stage of evolution between the higher and the 

 lower, cells were not present. 



The animal body, in Mr. Spencer's opinion, is a sort 

 of crystal It is to be regarded as compounded essen- 

 tially of " physiological units " of very highly complex 



