Chapter II 



EVOLUTION TRACED BIOCHEMICALLY 



A. B. Macallum 



THE cell, animal or vegetable, as we know it, is a com- 

 plex and highly developed chemical mechanism, 

 capable of continuing its Hfe, as it has done in a 

 suitable environment through eons of time, and transmitting 

 to its descendants the endowments of a far past. This suitable 

 environment did not always obtain for in the earliest age 

 of the earth the physical conditions on its surface were 

 vastly different from what they have been since and are 

 now. This at once suggests the question how and when did 

 life have its beginning. 



To conceive of an answer to this question, one must 

 concede that the cell has in its history undergone an evolution 

 the results of which have as greatly modified its structure and 

 characters as has evolution affected the multicellular forms of 

 animal and vegetable hfe. The units of primordial hving 

 matter must, therefore, as organisms, have been much 

 simpler chemically and structurally, and smaller in volume, 

 than existing ordinary animal and vegetable microorganisms. 

 We can, from what we know of the latter, predicate what 

 the primordial organism lacked as compared with the 

 Hving unicellular organism of today. 



First of all there was no nucleus in it. There are cellular 

 forms of hfe in which no nuclei exist, e.g. the blue-green 

 algae (Cyanophyceae), the moulds, and bacteria. Nuclei are 

 also wanting in certain Protozoa (e.g. Dileptus anser), in 

 certain others of which (Euplotes, Ceratium, Euglena, etc.) 

 the types of mitosis they exemphfy indicate that their nuclei 

 have not yet acquired the special characters of those found 

 in typical animal and vegetable cells, while in Calcituba 

 mitosis in any form, rudimentary or otherwise, does not 

 occur, the chromatin of its nuclei, when cell division begins, 

 segregating in a pecuHar fashion into a large number of 

 spherules from which new nuclei are formed. Indeed a 



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