OO Se ed eee Ea Lee ere et tena 
1909} GATES—CHROMOSOMES IN OENOTHERA 189 
as in my last paper in this journal (11), so that the figures can be 
directly compared. 
DISCUSSION 
The history of any ontogeny is the history of the transformation 
of chemical metabolism into definite structures, or rather the eventua- 
tion of a series of chemical processes in the production of a series of 
physical structures. Morphologists and cytologists map the succes- 
Sion of structures appearing and call it a series of events. They are 
not unmindful, however, that the primary process is the metabolism, 
the structures its by-products, which in turn, so far as they are ca- 
pable of continuing metabolism, produce other structures and, par- 
ticularly in the adult organism, structures like themselves. Similarly, 
the chromosomes of the germ nuclei must be thought of as definite 
aggregations of chemical materials, which initiate or take part in 
certain forms of metabolism. The chromosomes themselves do not 
(at any rate not wholly) control their growth or division, but this is 
more or less subject to the conditions of temperature, etc., in which 
they are placed, as the work of ERDMANN (7) and others has shown. 
Similarly, as the complex of physical and chemical conditions in the 
nucleus and cell undergoes changes, the chromosomes change from 
the compact to the alveolate or distributed condition, or vice versa, 
etc. The cytologists who record these events are aware that chemical 
transformations are continually going on, and that the changes in 
Visible physical structures are the external concomitant of such chem- 
ical processes. 
Chemical reactions in the test tube, however complex, do not lead 
to the production of any structures more complex than crystals or 
flocculent masses of various sorts. There are indications that living 
matter frequently has the properties of liquid crystals, but why do 
the infinitely more complex reactions of living matter build structures 
of such relative permanency and of tremendous intricacy? The 
problem of individual development, from this standpoint, is the ques- 
tion, How do certain forms of chemical metabolism result in the 
Production of certain visible physical structures or characters? Of 
Course, our present microscopic appliances do not permit us to know 
how many structural steps, if any, there may be between the inter- 
acting molecular masses and the finest structures visible under our 
