THE president's ADDRESS. 179 



tive and qualitative partition of the body during cell-division is 

 of extremely improbable occurrence, at least until the mechanism 

 of cell-division has reached its greatest perfection. The fact 

 that in the Infusoria, the most complex in structure of all the 

 Protista, syngamy is a frequent event and easy to observe, fits 

 in also with the view that sex-phenomena are in relation to 

 complication of cell-structure ; and conversely, the fact that in 

 Protozoa of simple structure, such as the B'lagellata, syngamy 

 is rarer and appears only to occur at long intervals in the hfe- 

 cycle, also receives a simple explanation. 



From all these facts and considerations, it appears extremely 

 probable that sex and syngamy in living beings was invented, 

 so to speak, when the cellular grade was evolved from the lower 

 or bacterial grade of structure. And this again is related, in 

 my belief, to another very important property of living things, 

 which I will indicate in brief outline. 



In the visible world of living beings, we find universally that 

 organisms are divisible more or less easily into groups which 

 we term species. As pointed out above, scientific and popular 

 opinion are more or less in accord on this point. To define a 

 species is difiicult, though to recognise one is in general not so. 

 Some species are more sharply marked off from others, some are 

 less so, and some are of questionable rank, regarded by one 

 naturalist as distinct, by another as a mere variety or race. No' 

 one now considers a species as a fixed and immutable entity. 

 Nevertheless, the fact remains that the tendency of living things 

 to separate themselves into species more or less distinct is one- 

 of the most constant and universal peculiarities of the organic 

 world. And when we turn to the invisible world of the Protista,, 

 we find again the same thing. The species of Protozoa and 

 Protophyta are just as distinct from one another, just as constant 

 in their characteristics, as those familiar to us in every- day 

 life. 



What is the bond whicli unites the individuals comprising a 

 species, and separates them from those of another, though 

 closely allied species ? So far as the Protista are concerned, I 

 believe it is nothing more nor less than syngamy, which checks 

 and restrains the tendency of individuals placed under slightly 

 different conditions of life to diverge from one another in 

 character. Without syngamy a species would tend to break up 



JouRN. Q. M. C, Series II. No. 68. 13 



