420 
Di D. FÉNYES 
which vary in the same or different directions and degrees ; the surplus 
of this generalization I intend to call the passive natural selec¬ 
tion, in contradistinction to the active natural selection, 
the meaning of which latter could be limited to the conditions, and its 
effect, to the adaptation. 
The following practical example will serve as an illustration of the 
above distinctions. The value of the modern show fox-terrier is decided 
first and foremost, irrespective of any of its other merits, by the straight¬ 
ness of the legs and the roundness of the feet. To preserve and improve these 
points, it is not sufficient to select the best and pedigree breeding, but a 
condition sine qua non is the keeping and exercising of the terriers and 
puppies consistently over the hardest possible ground, whereas, under 
the opposite,condition, viz., over a soft ground, the legs and feet soon 
spoil. Again, on the other hand, the size, shape and carriage of the fox 
terriers’ ears, being, under domestication, totally indifferent properties 
which vary independently of the conditions, can be perfectly regulated 
through artificial selection, or rather, by pedigree breeding. — In general, 
the regulation of the «adaptive» properties is a difficult, and that of the 
«indifferent» properties, an easy task from the breeders’ standpoint 
of view. 
All «adaptive» properties which are, under given conditions, advan¬ 
tageous or disadvantageous to their possessors can, in consequence of the 
changing of the conditions, become «indifferent» properties, and vice versa. 
Properties indifferent under domestication will be forced, when passing 
again into natural circumstances, to adapt themselves to the latter. 
Darwin’s Principles derived from the real facts and which always 
correspond to the latter are able to interpret, in the most conformable and 
natural manner, all the problem^ which were touched upon in this paper. 
In the idea of the «Pedigree Inheritance» I ventured as far as in me lay, 
to make out a uniform connection between the facts, the ground principle 
of evolution, the conception of variation, selection and heredity, in the 
Darwinian sense, and Haeckel’s fundamental biogenetic law, on the 
one hand, and, Galton’s law of ancestral inheritance and Mendel’s prin¬ 
ciples of heredity, both modified as in the present paper, on the other 
hand ; and I ventured at the same time, to try and point out, in accordance 
with the requirements of the ætiology, a uniform and natural cause of the 
phenomena which fall within the sphere of genetics. To my respected 
readers I leave the decision of the correctness of my conceptions as ex¬ 
pressed in this paper. 
There are no limits, definite ratios in living Nature ; there exist, on 
all its fields, changes, chances characteristic of the single cases, only. Here- 
