1894.] Limits of Biological Experiments. 845 
LIMITS OF BIOLOGICAL EXPERIMENTS: 
By Dr. Manty Mies. 
The proposition to test theories in evolution by direct exper- 
iments on living organisms which has been favorably noticed, 
and the numerous futile feeding experiments that have been 
made at the Government experiment stations, raise the ques- 
tion as to the probable limits of direct experimental methods 
in dealing with biological problems. The “whirligig of time,” 
in connection with a certain uniformity in the outcome of the 
modified processes of nutrition and reproduction in a number 
of individuals, must be regarded as essential elements in 
bringing about the gradual aggregation and perpetuation of 
the minute changes in living organisms which we recognize as 
processes of evolution. 
Aside from these significant factors, which cannot be 
neglected, the exceedingly complex conditiens involved in all 
biological activities appear to be formidable difficulties to 
‘overcome in attempting a direct experimental verification of 
theories relating to the various agencies concerned in evolu- 
tion, or, in determining the relative value of foods in the pro- 
cesses of nutrition. 
Intelligent breeders of domestic animals have no doubts in 
regard to the heredity of acquired characters, which, in the 
light of their experience, they look upon as a fundamental 
principle in stock breeding and one of the most important 
factors in the available means of improvement. The direct 
proof of this principle by experimental methods must, how- 
ever, be difficult, if not impossible, notwithstanding the 
cumulative and apparently conclusive evidence presented in 
the history of the improved breeds, and the experience of suc- 
cessful breeders who have recognized its importance in the 
improvement of their animals. 
The dominant influence of other known biological factors 
may completely obscure well marked special characters that 
‘(Abstract of a paper read at the Brooklyn meeting A. A. A. S., Aug., 1894). 
