74 'DETERMINANTS' VERSUS 



forms may be represented by the various kinds of Bacteria, of 

 Chromacea, or of simplest structureless AmcEbae. 



It must be clear from the point of view of Evolution that Uni- 

 cellular Organisms and the various developed forms of Cells 

 entering into the structure of multicellular plants and animals, are 

 products which have been evolved from structureless units of living 

 matter like one or other of the above-mentioned, lowest-known 

 forms of life, or units as simple as these. 



We have seen how freely the process of fission is capable of 

 taking place in all the lowest forms, in which no trace of a nucleus 

 exists ; how it occurs also in non-nucleated, filamentous Algae like 

 Vaucheria, and even in chlorophyll corpuscles — showing clearly 

 that this rudimentary ' reproductive process ' is in them essentially 

 dependent upon the molecular properties of the living matter itself, 

 and that it is not in relation with any visible structure. These are 

 facts only too much disregarded by many of those who base their 

 theories of Heredity upon what goes on in cells, and by others in 

 their attempts to establish a causal relation between some of the 

 processes occurring in an elaborately developed cell while it is 

 dividing, and going through all the mysterious changes included 

 under the term ' karyokinesis.' Formerly the nucleus, for instance, 

 was supposed to be the determining cause of this whole process, 

 but since the discovery in 1885 by Van Beneden of another product 

 of evolution in the cell, whose origin is still more mysterious, 

 namely, the "centrosome" the tendency has been to look upon this 

 minute body as the primary directing agent, in the various 

 processes occurring during the division of highly developed cells — 

 the changes in the nucleus and other parts occurring, as it were, at 

 its instigation. Whatever the interpretation of the relation between 

 the several processes may be, no one can study them without being 

 impressed by their truly wonderful nature, and without recognising 

 the complicacy of these processes of molecular physics which take 

 place during the life and multiplication of cells — bodies that were 

 formerly, though wrongly, regarded as the simplest of vital units. 



What has just been said may give a clue to the reason why there 

 are now two distinct biological schools in reference to the problems 

 connected with Heredity, and those developmental tendencies of 

 living matter that lie at the root of Evolution — tendencies which, 

 with other causes, have eventuated in the production of all the 

 forms of life that now exist, or in past ages have ever appeared, 

 upon the earth. There are those, for instance, who start in their 



