ZOOLOGY SINCE DARWIN. 489 



expedition has increased the number of known species in many groups 

 of animals four or five fold. 



The increase in the collective number of forms described has had, in 

 the first place, one result, in that it has obtained for the description of 

 species a wider basis and a more positive meaning, in contrast to the 

 Linnsean principle, that, looking only to practical exigencies of the 

 moment, declared that new species must be separated from those already 

 known by means of well-marked characters. We must now seek such 

 a conception of specific qualities as may enable us to separate each 

 specific form from those yet to be discovered. This requirement, which 

 was already considered by careful systematists before the time of Dar- 

 win, is especially difficult, and can not be met unless one possesses the 

 sense of form required for an artist. But at the same time the Dar- 

 winians often fell into a willful neglect of systematic work, a neglect 

 which arose from despising the hair-splitting systems of the museums 

 which were commonly unfriendly to the new theory, partly from exag- 

 gerated ideas of the fluidity of species — ideas which led to the most 

 extraordinary abortions in the systematic field. 



Happily, this period of fermentation is over, and we are learning 

 again to prize systematic description as it is, for example, employed in 

 the too long neglected science of entomology. We need these methods 

 not only for the purpose of lending depth to our studies through the 

 more extended retrospect of comparative anatomy and embryology, but 

 in order to better express, by means of a system, the natural relation- 

 ship of forms. One thing is certain, that the minutiose recital of diag- 

 nostically important external characters, which is customary in entom- 

 ology, has done much less harm than the neglect with which external 

 form relations have been treated by the u scientific" zoology of the last 

 ten years. To this neglect is to be ascribed the fact that modern mono- 

 graphs are almost useless for conscientious zoogeographers, because 

 they treat systematic subjects so superficially, and the reproach, some- 

 times not entirely without justice, is made against German zoology, 

 that it produces excellent theorizers, distinguished comparative anato- 

 mists and embryologists, but no zoologists. As if the knowledge of 

 form were not the basis of all zoology, and as if one could obtain a 

 living conception of the imenomena of variation without having trained 

 the eye by exact systematic studies in at least one group of animals ! 

 Darwin himself, at the very time when he was revolving in his mind 

 his undisclosed theory of natural selection, gave in his monograph on 

 the cirripeds, 1 an example of exact systematic description. And what 

 systematic zoologist does not know the important fact that there often 

 exists between apparently unessential external characters and impor- 

 tant points of internal organization so profound a correlation that 



'Charles Darwin, A Monograph of the subclass Cirripedia, with figures of all the 

 species. Two vols., London, 1851-1854. 



