K.—BOTANY. 255 
construction of its rooms and passages and the lighting of these by a 
few large windows or by many small ones, where the illumination 
required is equally well secured by either arrangement. I cannot here 
undertake a discussion of the justification for separating the ‘ characters’ 
of organisms into different categories, as Professor Gates, for instance, 
has tried to do,’? nor of the related controversy between those who 
believe that a ‘ particulate’ theory of inheritance such as that which 
has been worked out by the Mendelians is a sufficient basis for explain- 
ing all the phenomena, and those who advocate the claims of the organ- 
ism to be considered ‘ as a whole,’ which usually means in this connexion 
cytoplasmic inheritance, through the egg and perhaps sometimes also 
through the pollen. We cannot wholly exclude the possibility of 
cytoplasmic inheritance, or an eventual effect on the genotype of cyto- 
genetic characters; but from the broad position I am now taking I see 
no good reason for supposing that the ontogenetic development of what, 
for want of a better word, I may call ‘ organisatory ’ characters differs 
essentially from that of the characters which are commonly used to 
separate species and which obey the Mendelian laws. If we define a 
gene as some substance contained in the zygote which is a factor in 
the determination of the phenotype, we must believe that all hereditary 
phenotypic characters alike, internal or external, separating species or 
common to a great many species, important, indifferent, or disadvanta- 
geous in the life economy, are developed from the genotype, i.e. from 
the total stock of genes, whether contained in the chromosomes or not, 
by an inevitable series of chemical and physical processes, modified, of 
course, by differences of environment. Now my point is this. We can 
only hope to connect the genotype with the phenotype by tracing out 
these processes in detail, by following the cntogenetic history, not only 
in terms of the production of organs and tissues, of cell division and 
growth, but in terms of physical and chemical changes, of such processes 
as pressures and filtrations, oxidations and reductions, hydrolyses and 
condensations, reversible reactions and catalyses. And I think we may 
perhaps begin to find a way which will ultimately lead to an under- 
standing of how the genes produce the characters of the organism, and 
thus of the nature of the genes themselves, by following the trail which 
has recently been opened, by studying the detailed processes which lead 
up to the appearance of a structure, over and above, or, as one should 
perhaps more fittingly say, ‘ under and below,’ that reaction of struc- 
ture upon process which we have been used to call the ‘ function’ of 
the structure. It is only in this way, as TI believe, that we are likely, 
for instance, eventually to get more light on the problem of ontogenetic 
recapitulation, which has certainly not been rendered easier by the 
Mendelian results and the conception of the ‘ species cell.’ 
The botanists of seventy years ago, notably that great pioneer Sachs, 
in the spacious days of the new ‘wissenschaftliche Botanik’ in the 
fifties and ’sixties of the last century, had in some ways a view of the 
problems of structure clearer than that of their immediate successors. 
It is plain that the overwhelming effect of the theory of descent on the 
° R. R. Gates, ‘ Mutations and Evolution,’ New Phyt. 19, pp. 217 et seq., 1920. 
1923 T 
