74 LECTURES 



importance that has previously been written upon the 

 subject, or matter, or organism he proposes to examine; 

 next, to make that examination as carefully as possible, 

 and as thoroughly comparative as his material will ad- 

 mit, bringing to his aid the various modern instruments 

 of precision used by biologists or other scientists in their 

 own departments, and, finally, also summoning to his 

 assistance a clear knowledge of those natural laws as they 

 are at present understood and have bearing upon the 

 question in hand. To complete any such investigation 

 it should be printed, free from error, and in some medium 

 where it will become easily available for the students of 

 the future, and show upon every page, plate, and figure 

 of the record that its author had carried out in detail 

 every suggestion that I have just presented; that he has 

 properly accredited former workers in the same fields 

 with such facts as their prior labors revealed; that he is 

 candid, clear, thorough, logical, and guided by the desire 

 to discover only the truth in every detail to which he has 

 directed his mind during the task he has set himself to 

 perform. 



It goes without the saying that the principal field de- 

 manding the attention of the biologist is that one which 

 takes Into consideration the life-histories, morphology, 

 and physiology of all living animal organisms and plants. 

 Such studies are chiefly made in the biological laboratories, 

 the museums, and the zoological gardens, the former 

 always being properly fitted up with the proper ap- 

 pliances and text-books for that kind of research. 



Remembering now what has been said on the question 

 of the fundamental uniformity of structure, as exempli- 

 fied in the animal and vegetable kingdoms, it will at 

 once be appreciated that it obviates the necessity of the 

 student in zoology studying separately each and all the 

 entire series of species representing the existing world's 

 fauna on the one hand, and her flora on the other. We 

 can easily see how impossible such a task would be of ac- 

 complishment, inasmuch as there are considerably over 

 100,000 insects alone, and the species of plants in the 

 world is simply enormous. Fortunately, and taking in- 

 sects for example, which we have just mentioned, we 

 have such things as what may be regarded as more or 

 less type-forms in all the great groups of animals and 

 plants, and by making a proper selection of one of these 

 among the insects, and mastering all that can be known 

 of its life-history, structure, and so forth, it is quite 

 possible to gain a very fair conception of the correspond- 



