226 CONTRIBUTIONS TO THE NATURAL HISTORY 



get rid of the perplexity which attends tlie study of their complicated liistory, narrated as 

 it is under so different heads. Even at present, and with all the information we already 

 possess upon alternate generations, I find it most diflicult to impress naturalists, who have 

 devoted more attention to other branches of natural history, with the true view of this 

 subject. No doubt, the difficulty arises from the circumstance, that, in most cases 

 throughout the animal kingdom, all the individuals of the same species are so much alike 

 through their whole life, as to be easily combined in one comprehensive diagnosis 

 under a common generic and specific name. But whenever there are sexual distinc- 

 tions between individuals of the same species, we begin to meet with difficulties, as 

 there is a fatal propensity among observers to force their views upon nature, and to take 

 this or that form as most characteristic, and to mould the description accordingly, now 

 making the male, now the female, the type of the species ; describing almost as mere 

 occasional differences those constant and permanent peculiarities which characterize all 

 female individuals, or vice versa, as if, in different classes, males or females were more 

 prominent in their appearance ; as if it were not more correct and more in accordance 

 with nature to inention at once, that in such species males and females differ widely, the 

 males being distinguished by such and such characters, and the females by others, add- 

 ing, if necessary, a similar description of the young. 



Among animals which undergo extensive metamorphoses, the method of describing 

 formerly employed has become altogether useless. No philosophical observer will, in 

 future, be satisfied with a mere diagnosis of the winged state of a butterfly or a moth, 

 when he knows how characteristic, how peculiar, and how interesting the earlier stages 

 of growth of these animals are. I must confess that it gives to me personally as much 

 satisfaction to watch a caterpillar, to study its anatomical and physiological characters, 

 and investigate its zoological forms and peculiarities, to describe these details and com- 

 pare them with similar features observed in others, as I experience in investigating in the 

 same way either the chrysalis, or the perfect insect, or even the egg from which the whole 

 was derived. It is a great mistake to withhold the information acquired upon these differ- 

 ent points from our works on comparative anatomy, and to consider embryology almost as 

 a science by itself, unconnected with zorjlogy and comparative anatomy. Though the im- 

 portance of such combined studies is gradually felt more and more, the best evidence I 

 would adduce to show how little such views even now influence the progress of our sci- 

 ence will be seen by referring to our best and most recent text-books, both in zoology 

 and comparative anatomy. 



But just as zoologists have aimed always to refer their observations upon the different 

 Stages of growth of an individual species to the same systematic name, giving the ap- 



