1879. | i Ultimate Physical Unit of Living Matter. 19 
which show what a profound conception he possessed of the 
causal relations existing between the uses of parts and their de- 
velopment. Of recent authors, Darwin must occupy the first 
place, as many of his hosts of facts are admitted by him to bear a 
more or less distinctly dynamico-causal interpretation (vide, Varia- 
tion of Animals and Plants under Domestication). By far the most 
comprehensive principles of dynamical biology have, however, 
‘been suggested by Herbert Spencer, and they must be regarded 
as the first attempts at scientific presentation of the subject, in 
which, although the factors of the problem were not stated quanti- 
tatively in most instances, yet enough was said to show the appli- 
cability of the quantitative method. Besides these authors, more 
recent writers have begun to pay attention to the subject. Prof. 
Owen has for many years avowed his leaning to Lamarckianism. 
Prof. Jager,’ of Stuttgart, has written upon the influence of me- 
chanical strains in determining the length, etc., of bones. Prof. 
Lucae, of Frankfort, a. M., has also contributed to this subject. 
Gegenbaur, in his “ Elements of Comparative Anatomy,’ has nu- 
merous observations upon this subject. Prof. Cope may be added 
to this list, having contributed an article bearing solely upon this 
subject, to this journal, within the past year. This author, who, 
as we have seen, had already advanced views similar to Haeckel’s, 
which, if not as clearly expressed, were nevertheless published 
more than five years previously. These names show that I have 
not been alone in the study of animal metamorphosis as produced 
by means of dynamical agencies. I have always held that both 
the organism by means of its voluntary acts and -its passive sur- 
roundings reacted upon each other so as to produce morpho- 
logical and consequently structural changes. My short essay, 
“On the Laws of Digital Reduction,” which appeared in this 
Journal (Oct., 1877), and which was republished in the Kosmos, 
for 1878, illustrates what I- have just said. My papers on the 
“ Mechanical Genesis of Tooth-forms’’ also show the application 
of the method, besides minor papers on the mechanical differen- _ 
tiation of certain portions of the vertebral column, in this Journal — 
and Popular Science Monthly, 1877. 
The logical consequences of the acceptance of the Hypothesis 
1 Principles of Biology and also his Principles of Psychology. 
‘ parey Zeitschrift, BA. V.. 18 
c. Phila 
4 a ay 
. Acad. Nat. CE I sis. and the Dental Cosmos, 1878 (Etiotogi : > 
