20 MORPHOLOGICAL DEVELOPMENT. 



will be dominant characteristics. The physiological units 

 peculiar to each higher species will, speaking generally, 

 pass through this form of aggregation on their way towards 

 the final arrangement they are to assume; because those 

 primordial physiological units from which they are remotely 

 descended, aggregated into this form. And yet, just as in 

 other cases we found reasons for inferring (§ 131) that the 

 traits of ancestral organization may, under certain conditions, 

 be partially or wholly obliterated, and the ultimate structure 

 assumed without passing through them; so, here, it is to be 

 inferred that the process of cell-formation may, in some cases, 

 be passed over. Thus the hypothesis of evolution 



prepares us for those two radical modifications of the cell- 

 doctrine which the facts oblige us to make. It leads us to 

 expect that as structureless portions of protoplasm must have 

 preceded cells in the process of general evolution; so, in the 

 special evolution of each higher organism, there will be an 

 habitual production of cells out of structureless blastema. 

 And it leads us to expect that though, generally, the physio- 

 logical units composing a structureless blastema, will display 

 their inherited proclivities by cell-development and meta- 

 morphosis; there will nevertheless occur cases in which the 

 tissue to be formed, is formed by direct transformation of the 

 blastema.* 



* Let me here refer those who are interested in this question, to Prof. 

 Huxley's criticism on the cell-doctrine, published in the Medico- Chirurgical 

 Review in 1853. 



A critic who thinks the above statements are "rather misleading" ad- 

 mits that the lowest types of organisms yield them support, saying that 

 "there are certainly masses of protoplasm containing many nuclei, but no 

 trace of cellular structure, in both animals and plants. Such non-cellular 

 masses may exist during development and later become separated up into 

 cells, but there are certain low organisms in which such masses exist in the 

 adult state. They are called by some botanists non- cellular, by others 

 multi-nucleate cells. Clearly the difference lies in the criteria of a cell. 

 There are also some Protozoa, and the Bacteria, in which no nucleus has 

 certainly been demonstrated. But it is usual to consider the bodies of such 

 organisms as cells nevertheless, and it is supposed that such cells represent 



