318 Dr. T. Marg6 on the Classification 
Tn order to avoid as far as possible these and similar errors 
all earnest and prominent systematists seek the true character 
of a group of animals (species, genus, family, &c.) not in its 
individual peculiarities, but in a certain combination of all 
characteristic peculiarities ; that is to say, they found the cha- 
racter of the group upon a correctly combined summing-up of 
all its peculiarities, and, indeed, so that in each individual 
case the combined sum of the peculiarities always represents 
a definite animal-form, although the latter must not necessarily 
be assumed to be so unchangeable as was usual with the 
systematists of the old school. 
Nowadays, therefore, it could not occur to any thorough 
naturalist or earnest systematist to classify any group of 
animals in accordance with any exclusively external or inter- 
nal peculiarity observed either in an embryo, or in a larva, or 
in fully developed animals, with any one organic or biological 
condition. 
If we now put the question, how 7s a correct and really 
scientific classification of the animal kingdom to be created? 
we may be permitted, in connexion with this, to assume as a 
principle that a classification which, being based upon mor- 
phological and embryological facts, also takes sufficiently into 
account the paleontological and biological data, and carefully 
follows these facts step by step, must in any case lead with most 
certainty to the final aim of science. ‘This final aim is, how- 
ever, nothing else than the knowledge of the law in accordance 
with which, by means of inheritance and adaptation, animals 
have originated from each other. If this be correct (as to 
which, in the light of Darwin’s law of development, we cannot 
doubt for a moment), then such a classification of the animal 
kingdom, such a system, can alone be accepted as perfectly natu- 
ral, objective, and strictly scientific, which is capable of repre- 
senting, in the formof a genealogical tree, the origin and gradual 
development of the world of animals. 
Another question is, whether this ideal goal of our science 
will some day be really attainable, even after the labour of many 
generations. Among the younger zoologists there may per- 
haps be some who esteem it possible to attain to such a goal ; 
but if we seriously consider the many difficulties of this 
gigantic task and the insurmountable obstacles presented to 
it In certain directions, we must perhaps give up the hope 
that man, who in so many respects is able to govern nature, 
will really ever be in a position to construct a perfectly ob- 
