314 Dr. T. Margé on the Classification 
the enormous advance lately observable in the domain of mor- 
phology and embryology, an advance which from year to 
year becomes more and more evident by the discovery and 
exact observation and demonstration of new facts of great im- 
portance to science, which naturally lead to changes, modi- 
fications, and rectifications of opinion. From this it is easily 
understood why we meet with different systems in the different 
treatises and manuals of zoology, and how, even with the 
same naturalist, the system may change essentially from time 
to time. 
Thus, for example, Huxley’s system of the year 1875 is 
essentially different from that followed by him at a later 
period (1878) ; for while this naturalist formerly adopted the 
formation of the embryonal nutritive cavities, the mouth, and 
cceloma as the foundation for a phylogenetic grouping of 
animals, and accordingly divided the Metazoa into Archeo- 
stomata and Deuterostomata, and the latter again, in accord- 
ance with the mode of formation of the coeloma, into Kntero- 
coela, Schizoccela, and Epiccela, and consequently the whole 
animal kingdom into twenty-six stems or phyla*, the same 
author, some years later, leaving the phylogenetic point of 
view and the descent of animals entirely out of consider- 
ation, divided the whole animal kingdom, exclusively from 
morphological types, into eight large typical groups. We 
find similar alterations also more or less in the classifications 
of Gegenbaur, Ray Lankester, Claus, &c. 
Further vacillations of many kinds may also be produced 
in the system by the circumstance that the individual views 
of the different naturalists as to the value and usefulness of 
the facts ascertained by observation sometimes do not exactly 
agree, by which means the combinations and deductions from 
those facts may often lead to quite different final results. 
But if we consider not so much these combinations, but rather 
the already ascertained facts which constitute the proper sub- 
ject, the true foundation of classification, we come without 
much difficulty to see that the systems, however different 
they may be, nevertheless contain many generally admissible 
truths, which are raised beyond the least doubt. 
We may consider animals like all other natural objects— 
treat them systematically or group them from different points 
of view, and combine them at pleasure into a system. very 
zoological system, if it be objective and founded upon already 
demonstrated facts, has its justification, and when considered 
from a certain standpoint may have its value and use. ‘Thus, 
* Huxley, “On the Classification of the Animal Kingdom,” in Quart. 
Journ. Micr. Sci., January 1875, 
