30 NOMENCLATURE. 



mentioned above, shows the necessity of some element in common to 

 express the variable quantities constantly obtained in various departments 

 from a closer and more accurate examination of nature. This element 

 systematic Zoology furnishes; it gives us the quantities to make our equa- 

 tions, and when it takes this broad lbrm is no longer a mere dry collection 

 of meaningless names, but becomes our interpretation of nature. The 

 facility with which, in a new country, unknown animals can be described, 

 the notoriety thus readily obtained, is a strong incentive to descriptive 

 work ; not that I would, as is frequently done, deny all value to systematic 

 Zoology, but it should not be forgotten that the true purpose of useful 

 systematic work must be to increase our knowledge of the relationship of 

 animals to special groups already known, or serve in some way as a con- 

 necting link in the chain of the various branches of Zoology. We have 

 our independent memoirs of systematic Zoology, of Psychology, of Palaeon- 

 tology, of Comparative Anatomy, of Histology, etc., treating of their 

 respective sciences as isolated departments all strongly biassed by the 

 characteristics of the sciences from which they originated. Comparative 

 Anatomy and Physiology, as well as Histology, are the children of Human 

 Anatomy, and this, in its turn, was gradually developed from the needs of 

 Medicine. Embryology and Pahvontology, though so intimately connected, 

 are rarely treated together, the latter being considered to belong, by birth- 

 right, to Geology. Psychology is but now becoming emancipated from 

 speculative Philosophy. We have no recent Zoological memoir in the 

 Aristotelian sense ; the sciences forming the branches of Aristotelian Zool- 

 ogy stand upon separate pedestals. They have grown up independently 

 of one another, yet they all converge towards a common point, each an 

 important part in the life history of every animal; and the common link 

 which is to unite them all is (when rightly understood) systematic Zoology. 

 Working in this spirit, systematic Zoology helps us in our attempts to 

 understand the laws of nature; these must remain unintelligible to him 

 who is busy with naming and classifying materials, reducing his science to 

 an art, merely accumulating facts to be stored in museums, forming as it 

 were a library of nature. To him its books will be inaccessible, and its 

 laws as inexplicable as are the laws of the motions of the planets to one 

 who has no knowledge of the existence of gravitation. 



