CHAPTER IV. 



THE MORPHOLOGICAL COMPOSITION OF ANIMALS. 



§ 199. What was said in § 180, respecting the ultimate 

 structure of organisms, holds more manifestly of animals 

 than of plants. That throughout the vegetal kingdom the 

 cell is the morphological unit, is a proposition admitting of a 

 better defence, than the proposition that the cell is the mor- 

 phological unit throughout the animal kingdom. The quali- 

 fications with which, as we saw, the cell-doctrine must be 

 taken, are qualifications thrust upon us more especially by 

 the facts which zoologists have brought to light. -It is among 

 the Protozoa that there occur numerous cases of vital activity 

 displayed by specks of protoplasm; and from the minute 

 anatomy of all creatures above these, are drawn the numer- 

 ous proofs that non-cellular tissues may arise by direct meta- 

 morphosis of mixed colloidal substances.* 



* Since this paragraph was published in 1865, much has been learned con- 

 cerning cell-structure, as is shown in Chapter VI A of Part I. While some 

 assert that there exist portions of living protoplasm without nuclei, others 

 assert that a nucleus is in every case present, and that where it does not exist 

 in a definite aggregated form it exists in a dispersed form. As remarked in 

 the chapter named, " the evidence is somewhat strained to justify this dogma." 

 Words are taken in their non-natural senses, if one which connotes an indi- 

 vidualized body is applied to the widely-diffused components of such a body ; 

 and this perverting of proper meanings leads to obscuration of what may 

 perhaps be an essential truth. As argued in the chapter named (§§ *74e, 74/*), 

 nuclear matter is, as shown by its chemical character, an extremely unstable 

 substance, the molecular changes of which, perpetually going on, initiate 



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