No. 6. — Studies in Morphogenesis. — IV. A Preliminary Cat- 
alogue of the Processes concerned in Ontogeny. By C. B. 
DAVENPORT. 
CONTENTS. 
Pace 
Introduction: Limitations of the Paper . . . . . . 2 2 2 2 2 2 es 178 
A. General Ontogenetic Processes . . . . . . 2 2 2 . 4... .. 174 
B. Special Ontogenetic Processes . . . . 174 
I. Ontogenetic Processes occurring in Migratory Protoplasmio Bodies 
(Mesenchyme) . . Krise, b 
II. Ontogenetic Processes occurring in in Elongated Piloplainfó Bodies 
(Fibres, Threads, Cords, Tubules) . . . si oe ee ALSO 
III. Ontogenetic Processes occurring in Protoplasmic Taras sra WBE 
IV. Ontogenetic Processes occurring in Protoplasmic Masses . . . . 192 
Recapitulation and General Remarks. . n s . s s wte e s op a o 19 
Most important perhaps of all the problems which the biologist sees 
lying unsolved before him is that of the development of the individual, 
— a problem to which, from the time of Aristotle, zoólogists have re- 
peatedly turned, although scarcely hoping for its eventual solution. 
Without attempting to consider the various theories of Outomorpho- 
genesis which have at different times been offered, it is sufficient to state 
that it is now generally agreed that ontogenesis is a process, or rather a 
complex of processes, taking place in the protoplasm of the developing 
individual. 
Now it is a highly probable belief that no movement takes place in 
protoplasm except as a response to stimuli. The very fact that onto- 
genesis is a complex of actions indicates that there must be a large 
number of stimuli raining in upon the different parts of the developing 
protoplasm to which they respond. 
In order to gain some idea of what the stimuli are, it is first neces- 
sary to analyze the ontogenetic complex of prooesses into its simple 
elementary ones. 
It is the aim of this paper to make such an analysis into the elemen- 
tary ontogenetio processes as a basis for determining the nature of the 
exciting stimuli. 
1 Contributions from the Zoölogical Laboratory of the Museum of Comparative 
Zoology at Harvard College, E. L. Mark, Director, No. L. 
VOL. XXVII. — NO. 6. 1 
