BRANCHES OF THE ANIMAL KINGDOM. 215 



in distinct moulds or forms. 1 Now there can certainly be 

 no reason why we should not all agree to designate as types 

 or branches all such great divisions of the animal kingdom 

 as are constituted upon a special plan, 2 if we should find 

 practically that such groups may be traced in nature. 

 Those who may not see them may deny their existence ; 

 those who do recognize them may vary in their estimation 

 of their natural limits ; but all can, for the greatest benefit 

 of science, agree to call any group which seems to them 

 to be founded upon a special plan of structure, a type or 

 branch of the animal kingdom ; and, if there are still 

 differences of opinion among naturalists respecting their 

 limits, let the discussion upon this point be carried on 

 with the understanding that types are to be characterized 

 by different plans of structure, and not by special ana- 

 tomical peculiarities. Let us avoid confounding the idea 

 of plan with that of complication of structure, even 

 though Cuvier himself has made this mistake here and 

 there in his classification. 



1 It would lead me too far were I sions, in a somewhat modified sense, 

 to consider here the characteristics is found preferable to framing new 

 of the different kingdoms of Nature, ones. I trust the value of the fol- 

 I may, however, refer to the work of lowing discussion will be appreciated 

 I. GEOFFROY ST. HILAIRE, Histoire by its intrinsic merit, tested with a 

 naturelle generale des regnes organ- willingness to understand what has 

 iques (Paris, 1856, 8vo.), who has been my aim, and not altogether by 

 discussed this subject recently,though the relative degree of precision and 

 I must object to the admission of a clearness with which I may have ex- 

 distinct kingdom for Man alone. pressed myself, as it is almost ^impos- 



2 It is almost superfluous for me sible, in a first attempt of this kind, 

 to mention here that the terms, plan, to seize at once upon the form best 

 ways and means, or manner in which adapted to carry conviction. I wish 

 a plan is carried out, complication of also to be understood as expressing 

 structure, form, details of structure, my views more immediately with re- 

 ultimate structure, relations of indi- ference to the animal kingdom, as I 

 viduals, frequently used in the fol- do not feel quite competent to extend 

 lowing pages, are taken in a some- the inquiry and the discussion to the 

 what different sense from their usual vegetable kingdom, though I have 

 meaning, as is always necessary when occasionally alluded to it, as far as 

 new views are introduced in a sci- my information would permit, 

 ence, and the adoption of old expres- 



