THE MORPHOLOGICAL COMPOSITION OF PLANTS. It3 



tiation 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 physiolo 

 gical 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. 



Interpreting the facts in this manner, we may recognize 

 that large amount of truth which the cell-doctrine contains, 

 without committing ourselves to the errors involved by the 

 sweeping assertion of it. We are enabled to understand how 

 it happens that organic structures are usually cellular in their 

 composition, at the same time that they are not universally 

 so. We are shown that while we may properly continue to 

 regard the cell as the morphological unit, we must constantly 

 bear in mind that it is such, only in a greatly-qualified sense.* 



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

 ley s criticism on the cell-doctrine, published in the Medico -Chirurgical lievw* 

 in 1853. 



