IN RELATION TO ORGANISED BEINGS. 41 



proving the science, none has yet discovered a good structural prin- 

 ciple upon which to establish the genuine classes of vfhat we must be 

 allowed to call the vegetable sub-kingdoms. It is somewhat remark- 

 able, too, that our success has been greatest with the lowest of the 

 three, for Thallogens are certainly a class, and if we distinguish Ano- 

 gens from Acrogens, by characters founded on both the nutritive and 

 reproductive systems, which seem sufficient, guarding ourselves from 

 the error of confotinding the Ferns with Endogens on account of their 

 imperfect vascular system, we have three natural and well defined 

 classes of Acotyledonese which again subdivide into alliances and 

 orders, in a manner, which makes the classification convey the sub- 

 stance of our knowledge, and afford the best aid to our minuter 

 studies. 



I must now direct your attention to the state and progress of classi- 

 fication in the animal kingdom. There was little that could be called 

 progress from Aristotle to Cuvier. Linnaeus' Zoological system was 

 a very inferior one. Cuvier's improvements were founded on the 

 study of organization in every department of the animal kingdom, and 

 though so much has been done since he commenced his labours, cor- 

 recting errors, perfecting details and extending the field of observa- 

 tion, his grand divisions of animals, known as sub-kingdoms or 

 branches, are still accepted by most Zoologists with or without the 

 addition of a fifth, which the advance of microscopical studies has in 

 the opinion of many proved to be necessary. La Marck took as a 

 leading division that between Vetebrate and Invetebrate animals — 

 a real one doubtless in a certain sense, but which ignored the impor- 

 tant fact that, any of the other divisions might, with equal propriety, 

 have been insulated and opposed to the rest — that the difference in 

 essential structure between Articulates and Molluscans is quite as great 

 as that between Vertebrates and either of them. So true is this that 

 the expression Invertebrate animals, much used since LaMarck's 

 writings conveys a misleading and confused idea, and ought to be 

 carefully avoided. It does not enter into my plan to criticise the 

 schemes of particular zoologists, but rather to refer to different tend- 

 encies of thought in respect to zoological classification, and estimate 

 their influences in leading towards a truly natural system. The great 

 philosophical naturalist of Germany, Oken, though guided to a great 

 degree by his extensive and accurate knowledge of structures, founded 

 his system on a preconceived idea of what must be or ought to be, in 



