20 PRESIDENT’S ADDRESS, 
ments of the parental nuclei is related to the transmission of parental 
qualities. | But we must not be blind to the possibility that these 
transmitted qualities may be connected with specific chemical charac- 
ters of the transmitted elements; in other words, that heredity also is 
one of the questions the eventual solution of which we must look to the 
chemist to provide. 
So far we have been chiefly considering life as it is found in 
the simplest forms of living substance, organisms for the most part 
entirely microscopic and neither distinctively animal nor 
aia vegetable, which were grouped together by Haeckel as 
; a separate kingdom of animated nature—that of Protista. 
But persons unfamiliar with the microscope are not in the habit of 
associating the term ‘ life ’ with microscopic organisms, whether these 
take the form of cells or of minute portions of living substance which 
have not yet attained to that dignity. We most of us speak and think 
of life as it occurs in ourselves and other animals with which we are 
familiar; and as we find it in the plants around us. We recognise it 
in these by the possession of certain properties—movement, nutrition, 
growth, and reproduction. We are not aware by intuition, nor can 
we ascertain without the employment of the microscope, that we and all 
the higher living beings, whether animal or vegetable, are entirely 
formed of aggregates of nucleated cells, each microscopic and each 
possessing its own life. Nor could we suspect by intuition that what 
we term our life is not a single indivisible property, capable of being 
blown out with a puff like the flame of a candle; but is the aggregate 
of the lives of many millions of living cells of which the body is com- 
posed. It is but a short while ago that this cell-constitution was dis- 
covered: it occurred within the lifetime, even within the memory, of 
some who are still with us. What a marvellous distance we have 
travelled since then in the path of knowledge of living organisms! The 
strides which were made in the advance of the mechanical sciences 
during the nineteenth century, which is generally considered to mark 
that century as an age of unexampled progress, are as nothing in 
comparison with those made in the domain of biology, and their 
interest is entirely dwarfed by that which is aroused by the facts relat- 
ing to the phenomena of life which have accumulated within the same 
period. And not the least remarkable of these facts is the discovery of 
the cell-structure of plants and animals! 
Let us consider how cell-aggregates came to be evolved from 
organisms consisting of single cells. Two methods are possible— 
viz. (1) the adhesion of a number of originally separate 
ie ig of individuals; (2) the subdivision of a single individual with- 
ugeregate, out the products of its subdivision breaking loose from one 
another. No doubt this last is the manner whereby the 
