166 GILBERT C. BOURNE. 
prejudice to the metaphysical standpoint, we must conceive 
that what is capable of giving rise in us to such very distinct 
sensations, must have a real existence. I am referring now to 
the component parts of the tissues of higher animals and plants, 
and not to unicellular organisms. 
If, then, the thing has existence, it must have attributes ; 
we must be able to affirm something of it. What we have to 
affirm is not the attributes of this cell or of that cell, but of 
cells in general. We have to give expression to a morpho- 
logical idea, in the sense in which Goethe used the word 
morphological. Our concept of a cell must be an “ Allgemeines 
bild,’ the generalised idea of a cell, derived from our ex- 
perience of many kinds of cells. I have already shown, at 
sufficient length, that we must now regard something of the 
nature of a nucleus as an essential component of all cells, but 
as the concept of a nucleus as a central organised body is not 
applicable to all cells, I would widen Max Schulze’s definition 
by saying that “a cell is a corpuscle of protoplasm, which 
contains a specialised element, nuclein.”” This is a sufficiently 
comprehensive statement of our “ Allgemeines bild,” though 
I cannot pretend that it is not open to objection. 
Cells, as thus defined, are not only of various kinds, but 
they are variously compounded together. We may, by the 
process of dichotomous division, classify them, according to 
their relations to other cells, as discrete and concrescent. 
By discrete cells, I] mean those whose protoplasm is not 
in union with that of any other corpuscle. 
By concrescent cells, I mean corpuscles whose protoplasm 
is in union with that of other corpuscles. 
Discrete celis may further be divided into: 
Independent cells, living wholly apart from one another, 
or separated by an appreciable interval of space, e.g. uni- 
nucleate Protozoa, the mature ovum, leucocytes. 
Coherent cells, which are in close apposition to others, 
but not organically in union with them, e.g. the blastomeres of 
many developing embryos. 
Concrescent cells may also be further divided into : 
