MODERN BIOLOGICAL INQUIRY. 291 



At the same time, for this investigation, the study of insects is 

 peculiarly suitable ; not only on account of the small size, ease of 

 collecting, and little cost of preserving the specimens, but because 

 from their varied mode of life in different stages of development, and 

 perhaps for other reasons, the species are less likely to be destroyed 

 in tlie progress of geological changes.* Cataclysms and sul)mer- 

 gences, which would annihilate the higher animals, would only float 

 the temporarily asphyxiated insect, or the tree-trunks containing the 

 larvB and pupte, to other neighboring lands. However that may be, 

 I have given you some grounds for believing that many of the spe- 

 cies of insects now living existed in the same form before the appeai*- 

 ance of any living genera of mammals, and we may suppose that their 

 unchanged descendants will probably survive the present mammalian 

 fauna, including our own race. 



I may add, moreover, that some groups, especially in the Rhyncho- 

 phora, which, as I have said above, I believe to be the earliest intro- 

 duced of the Coleoptera, exhibit with compact and definite limits, and 

 clearly-defined specific characters, so many generic modifications, that 

 I am compelled to think that we have in them an example of the long- 

 sought, unbroken series, extending in this instance from early meso- 

 zoic to the present time, and of which very few forms have become 

 extinct. 



I have used the word species so often, that you will doubtless be 

 inclined to ask, What, then, is understood by a species ? Alas ! I can 

 tell you no more than has been told recently by many others. It is 

 an assemblage of individuals, which difier from each other by very 

 small or trifling and inconstant characters, of much less value than 

 those in which they difier from any other assemblage of individuals. 

 Who determines the value of these characters ? The experienced 

 student of that department to which the objects belong. Sjoecies are, 

 therefore, those groups of individuals representing organic forms 

 which are recognized as such by those who from natural power and 

 education are best qualified to judge. 



You perceive, therefore, that we are here dealing with an entirely 

 ditierent kind of information from that which we gain from the phys- 

 ical sciences ; every thing there depends on accurate observation, 

 with strict logical consequences derived therefrom. Here the basis 

 of our knowledge depends equally on accurate and trained observa- 

 tion, but the logic is not formal but perceptive. 



This has been already thoroughly recognized by Huxley "^ and 



' For a fuller discussion of these causes, and of several other subjects which are 

 briefly mentioned in this address, the reader may consult an excellent memoir by my 

 learned friend Mr. Andrew Murray, " On the Geographical Relations of the Chief Co- 

 leopterous Faunae." {Journal of Linncean Society, Zoology, vol. xi.) 



* " A species is the smallest group to which distinctive and invariable characters can 

 be assigned." ("Principles and Methods of Paleontology," Smithsonian Report, 1869, 

 p. 378.) 



