162 ROYAL SOCIETY OF CANADA 



only a few of them may have the affmity for the material of the nuclear 

 membrane which will enable them to jiass through the latter. Miescher 

 has pointed out that when an organic compound, e.g., albumin, has at 

 least 40 ajtoms of carbon, a billion isomers of it are possible and this 

 number may be greatly increased by variations in the position of the 

 nitrogen atoms. How this may permit variations in the offspring while 

 providing for transmission of the general characters need not be dis- 

 icussed here. 



Tbe nuclear membrane, therefore, makes the transmission of an- 

 cestral characters from generation to generation possible. The nucleus, 

 membrane and contents, has thus been of 'immense service to organisms 

 in the struggle for existence^ for if the germ plasma, the particular iron- 

 holding nucleoprotein which is the all-important element in heredity, 

 were freely exposed in the cell protoplasm, it would be subject to changes 

 which the never-ending chemical processes in the cell would bring about, 

 and it would also, be affected by the salts constantly diffusing 

 through th€( cytoplasm. That such salts would be hannful may be in- 

 ferred from the fact that they do not occur in the nucleus. Any changes 

 ithait would give rise to variations in the species must arise through a 

 germ plasma being -laltered in composition, but to such a slight extent 

 that it still is soluble in the nuclear membrane and therefore penetrates 

 to the nujclear cavity, and in consequence the offspring of the next genera- 

 tion would be somewhat different. Such slight changes in the germ plasma 

 would be cumulative, would result eventually in such a change in the 

 nuclear membrane as to permit only the germ plasmia resulting from 

 such cimiulative action to enter the nuclear cavity and thus a new species 

 with more or less fixed characters would originate. Thus, without a 

 nucleus, there could be no fixity of type or of charaoters. Whatever char- 

 acter one generation in a species would win that would be of advantage 

 to it in the struggle for existence, could not be continued unchanged in 

 'the next or irt might not be transmitted. In this way chaos might result 

 and there would be no progress or development such as there has been in 

 ervolution. 



This constitutes the reasion why the species of nucleated organisms 

 vastly out-number the non-nucleated. In the early history of life on 

 the globe all organisms were non-nucleated, but gradually some unicel- 

 lular forms developed a nucleus which gave them an immense advantage 

 hi evolution, and these throve and displaced the non-nucleated forms. 

 Of the latter, there now remain only the yeasts, bacteria and the blue- 

 green algae. The yeasts and bacteria have an external membrane which 

 seems to have many but not all of the properties of a nuclear membrane. 



