XXXVI PROCEEDINGS OP THE GEOLOGICAL SOCIETY. 



extend the limits to include a whole natural genus ; others contract 

 them to species, and these very narrowly defined. 



§ Provinces in Time. 



Geologists have generally accepted these views, as they have done 

 in regard to fixed truths of chemistry and mechanics ; and they have 

 added, from the evidence which their peculiar studies yield, a definite 

 origin of each natural group in time, the approximate duration of 

 the life of many, and the epochs of termination of several. Thus 

 every specific form is conceived to have sprung into heing at a 

 certain point on the globe, at a definite epoch of time ; its existence 

 is traced through provinces of space and through periods of time, so 

 that it has a real physical history. 



For those who adopt this view, the course of reasoning on the 

 succession of life on the globe is clear and convincing. It is, how- 

 ever, not universally adopted ; but the hypotheses which have been 

 framed to replace it (which always involve the idea of indefinite 

 change of form, structure, and habits) would not, if adopted, materially 

 affect the conclusions of geology, or change the practice of naturalists. 

 If it is by the course of progressive change from older types that 

 new specific forms have arisen, there must have been for each of 

 these a time and a place when it began to manifest the new specific 

 distinction. Geology needs not to discuss these hypotheses, sanc- 

 tioned though they be by eminent names, amongst whom our Darwin 

 is preeminent for powers of generalization operating on a large 

 basis of personal observation*. None of them appear to be wholly 

 without a foundation of fact, though none of them can be held to 

 penetrate more than a small way into the mystery of the origin of 

 species. "We may grant, with Lamarck, the inherent power of an 

 organic body to undergo some change, or to effect some self-develop- 

 ment, by reason of the intensive or abnormal exercise of its organs ; 

 we may allow to external conditions some influence in modifying 

 the sensible characters of species, which is so boldly claimed by the 

 author of the * Yestiges of Creation ; ' and we may agree with Mr. 

 Darwin in his more practical view of the derivation of some specific 

 forms of one period from others of earlier date by descent with 

 modification. We may accept all this, and yet consistently retain 

 the conviction that the changes which are possible by such causes 

 are circumscribed within the many essential types of structure which 

 appear to be a part of the plan of creation f. 



* The work of this author on Fossil Cirripedia is one of the most remarkable 

 examples of his former careful discrimination of species (Pala?ont. Soc.) ; while 

 his latest publication, ' On the Origin of Species,' is the most elaborate essay yet 

 produced in favour of the descent of all known forms of life from a small 

 number of originally created types. 



t In the following words of Linnaeus, the attentive reader will perceive proof 

 that some of the questions, now agitated with so much interest, have not been 

 neglected by this great " Minister and Interpreter of Nature" :— 



" Supponas D. O. O. in primordio e simplici progressum ad composita ; e paucis 

 ad plura ! adeoqtie a primo Vegetabili principio, tot tantum creasse plantas 

 diversas, quot ordines Naturales. Has ordinum plantas IPSUM dein ita 

 inter se generando miscuisse, ut totidem exorirentur planta? quot hodie distincta 



