CLASSIFICATION OF ANIMALS. 197 



agreement of our conclusions, wliether derived from anatomical evi- 

 dence, from embryology or from palaeontology. Nothing, indeed, 

 can be more gratifying than to trace the close agreement of the 

 general results derived from the study of the structure of animals, 

 with the results derived from the investigation of their embryonic 

 changes, or from their succession in geological times. Let anatomy 

 be the foundation of a classification, and in the main, the frame thus 

 devised will agree with the arrangement introduced from embryo- 

 logical data. And, again, this series will express the chief features 

 of the order of succession in which animals were gradually intro- 

 duced upon our globe. Some examples will show more fully that 

 this is really the case. Resting more upon the characters derived 

 from the nervous system, Avhich in the crabs is concentrated into a 

 few masses, zoologists have generally considered these animals as 

 higher than the lobsters, in which the nervous ganglia remain more 

 isolated. Now as far as we know, the embryos of brachyuran Crus- 

 tacea, that is, of crabs, are all macrural in their shape, that is to 

 say, they resemble at an early age the lobsters more than their own 

 parents ; and again, lobster-like Crustacea prevailed in the middle 

 ages of geological times during the triassic and oolitic periods, that 

 is, ages before crabs were created, as we find no fossils of that family 

 before the tertiary period. 



Of the class of insects I have for the present little to say, the di- 

 versity of their metamorphoses having not yet allowed an insight into 

 their bearing. I will only mention that the predaceous character of 

 the larvse of most of the sucking insects, which are provided with 

 powerful jaws in their early stages of growth, seems to indicate that 

 the chewing insects rank lower than the sucking tribes. Investiga- 

 tions which I am tracing at present, will, I hope, throw some light 

 upon this most important question.* 



* Since the above remarks were written, I have devoted most of my time to the in 

 vestigation of these metamorphoses in insects ; and to my great satisfaction (but, I 

 may say, as I anticipated,) I find that the metamorphoses of the higher insects throw 

 such light upon the real relations of the different orders of that class, as to settle final- 

 ly the question of their gradation. It has now become with me a matter of fact, that 

 Coleoptera, Orthoptera, Neuroptera and Hymenoptera, rank below Hemiptera, Diptera 

 and Lepidoptera. A careful investigation of the changes of Lepidoptera has shown to 

 me that, prior to assuming its pupa form, the young butterfly assumes, under the last 



