978 
embryonic stages; such facts do not, how- 
ever, establish a general law of retrogres- 
sion or recapitulation, since the metamor- 
phoses of insects and other similar phenom- 
ena show that evolutionary deviations and 
adaptations may occur at any stage in the 
life histories of organisms. 
The adaptability of an organism is in 
general inversely proportional to the degree 
of ecological specialization already attained. 
Accordingly, highly specialized types tend 
to become restricted and to disappear, while 
the more primitive may persist and give re- 
peated demonstrations of the evolutionary 
tendencies or variational possibilities of the 
group. 
Parallel evolution is thus not necessarily 
adaptive or mimetic, and may often be in- 
terpreted as an indication that a tendency 
to a particular variation may outlive specific 
differentiation and become similarly accen- 
tuated, even in groups in which long sepa- 
ration has permitted the accumulation of 
many differences in other characters. 
From the standpoint of a kinetic theory 
the inheritance of acquired characters be- 
comes a purely formal question ; indeed, it 
may be said that the origination and inheri- 
tance of characters are but different state- 
ments of the same fact, since characters 
originate and are extended because of the 
same inherent tendency to change. 
The continued differentiation of vestigial 
organs and structures shows that there is 
no essential connection between evolution 
and use. 
and specific differences are also obviously 
non useful ; they arise, are prepotent and 
are perpetuated because they are different 
and new, rather than through any external 
influence or necessity. 
All hereditary characters are acquired, 
but not all acquired characters are heredi- 
tary. There is no reason to believe that 
any are hereditary which have not been 
acquired through the assistance of normal 
SCIENCE. 
The vast majority of variations. 
[N.S. Vou. XIII. No. 338. 
variation. Mere mutilations or reactions 
to external conditions are not hereditary. 
Evolution is essentially a process of acquir- 
ing characters, but no direct nexus between 
environment and heredity has been demon- 
strated, and none is necessary under a ki- 
netic theory. 
A kinetic theory enables us, in short, to 
recognize the varied facts of evolution with- 
out doing violence to any of them. While 
holding that all evolutionary changes are 
essentially the same in having an internal 
and spontaneous origin, we are still not com- 
pelled to deny that adaptations have been 
influenced by external agencies. Selec- 
tion represents, however, not the causes, but 
the external incidents of evolution. Per- 
sistent variation should be compared with 
the main spring, selection to the balance- 
wheel, of an organic creation which pro- 
gresses because new characters and powers 
are welcome, rather than because old types 
are exterminated. 
O. F. Coox. 
WASHINGTON, D. C. 
THE LATE MILES ROCK. 
Mites Rock, a notable scientist, born 
at Ephrata, Lancaster county, Pennsyl- 
vania, October 10, 1840, died on January 
29, 1901, in his sixty-first year. 
During boyhood he attended the public 
schools of Ephrata, and later the Lancaster 
High School, fitting himself for Franklin 
and Marshall College. At the outbreak of 
the Civil War he was pursuing his studies 
at this college ; but love of country and the 
trend of public spirit at the time prompted 
him to join the Pennsylvania Volunteers 
and proceed to the seat of war. He re- 
mained a soldier at the front until the close 
of the war ; and it is significant of his char- 
acter that he carried in his knapsack a 
copy of Gray’s ‘ Manual of Botany,’ and em- 
ployed his leisure in collecting and analyz- 
ing the plants observed in the campaign. 
