TEREBRATULA. 213 



It is quite certain that too little attention is given to the many modifications of which 

 a species is susceptible ; this Tact has been clearly demonstrated by Dr. Carpenter in his 

 admirable researches among the Poraminifera, and will be easily exemplified by the 

 Brachiopoda, which are traceable through the entire series of fossiliferous rocks. 



Two opinions appear to prevail at the present time on the origin of species. The 

 greater number of naturalists believe in the creation of separate forms or species capable 

 of producing varieties, but to how great an extent he who made them only knows. Darwin, 

 on the contrary, supposes all species to have been derived from a common progenitor, but 

 to be able to positively admit or refute such an idea, it would be necessary to possess a far 

 more extended and minute knowledge of species, and the causes of their variation, than 

 we at present possess; and although I could not conscientiously go the full length 

 with Darwin, I heartily concur with Prof. Huxley, while observing that " all competent 

 naturalists and physiologists, whatever their opinions as to the ultimate fate of the 

 doctrines put forth, acknowledge that the work in which they are embodied is a solid 

 contribution to knowledge." I will not therefore follow those, who blindly admit the 

 theory, nor concur with those who unhesitatingly pronounce it a chimera, but will do my 

 utmost to register the great facts as they stand, with such comment as I can give, and we 

 may thus be led by degrees to a better understanding of many problems relating to species 

 and their origin than we at present possess. Palaeontologists should, above all, be zoologists, 

 and as zoologists have little to do with geological divisions or systems ; when they have to 

 inquire into the resemblances and variations in species they should always endeavour to 

 trace a species through its many modifications as far back as they can, or, in other words, 

 to search for its probable progenitor, be it located in the Carboniferous, Devonian, Silurian, 

 or in any other system of strata, as well as to follow or trace its recurrence in more recent 

 periods, and I may boldly assert that when our knowledge of the Brachiopoda shall have 

 extended, that the intimate connexion of many of the so-termed species will be discovered, 

 and that a large proportion of them will be traced through their various modifications to 

 a parent form in stages far more ancient than we are in many cases disposed to admit. 



Before concluding, let me therefore recapitulate the result of five years' attentive study 

 of the British Carboniferous species, and point out, however imperfectly, as far as our 

 means will permit, those points which appear to have been clearly made out, as well as 

 some of those I am necessarily compelled to leave unsettled, for I am far from 

 believing that we have arrived at finite or satisfactory results, with reference to several of 

 the species. 



Terebratula (pp. 11 — 18). Plate I and XLIX. 



In 1857 I described T. hastata, T. sacculus, T. Gilling crisis, and T. vesicularis, as 

 distinct species, but the subsequent study of a very considerable number of specimens of 



