THE STRUCTURE OF PROTOPLASM 
281 
stage, though his figures are clear enough for Daphne and Hyacinthus, cannot 
be regarded to-day as completely convincing in spite of the quasi support his 
theories have received from the theory of the mitochondrial origin of all plas- 
tids. In such forms as Hydrodictyon the division of the chlorophyl-bearing 
plasm is the division of the primordial utricle itself, but in the division of the 
tissue cells of the higher plants the independent constriction and bipartition of 
the plastid as such is to be reckoned with as a cytological fact of the first 
significance, and we must simply confess that we know nothing of the fun- 
damental physical-chemical processes by which such constrictions are 
initiated and carried through. Our increasing knowledge of the chemistry 
of the carbohydrate and protein molecules has given us no clue to the solution 
of the problem of division, whether in the case of the simple bipartitions of 
these plastids or the complex mechanical processes involved in karyo- 
and cytokinesis. Under such circumstances, however, it is worse than 
useless to use such phrases as ''tendency of protoplasm to divide" or "ten- 
dency of living materials to reproduce by bipartition." The problem is to 
be attacked, as it seems to me, from the standpoint of the newer evidence 
and conceptions as to the physical conditions existing in polyphase and 
compound colloidal systems rather than from that of a study of the chemical 
organization of the protein molecule. 
Our knowledge of the visible structures concerned with oil and carbohy- 
drate formation in the cell, as well as our knowledge of the sources of the 
materials and the possible chemical stages in the synthesis of starch from 
CO2 and H2O, give us a standpoint from which to obtain suggestions as to 
the organization of protoplasm and indicate the progressive localization 
of these processes in the protoplasmic mass with the formation of more 
and more definitely differentiated organs which finally reproduce by division. 
In sharpest contrast with these contributions of cytology to our knowl- 
edge of oil a'nd carbohydrate formation in the cells, I would set much of the 
modern literature of the chondriosomes, mitochondria, etc. Here, it seems 
to me, instead of a critical study of protoplasmic structure in relation to 
cell functions, we have in too many cases a mere reactionary movement 
taking its origin in the old view that we should hope to find in the cell the 
physical embodiments of the gemmules, pangens, ids, plastidules, etc., of 
a generation past. In so far as Meves, Duesberg, and others have endeavored 
to associate the formation of muscle rods, nerve fibrillae, etc., with visible 
elements of the embryonic cytoplasm, their work is, of course, highly sug- 
gestive and stimulating. I do not wish now to attempt to pronounce a 
judgment on the evidence as given by the authors noted above as to the 
relation of so-called chondriosomes, mitochondria, etc., to the processes 
of cellular differentiation in animal tissues. Their figures are in some 
degree at least convincing, and if confirmed will, in my opinion, mark one 
of the longest forward steps that have yet been taken in our investigation 
of the physical basis of life and life processes. Much less satisfactory is 
