“We find that the large number of genera made their first appearance during the Palæozoic periods, and since they have been decreasing in number to the present period. We will leave out of question the species, for they vary so little that it is often very difficult to trace really good distinctive characters between them; it is different with the genera, as they are, or should be, founded on much greater and more permanent distinctions. Thus, for example, the family _Spiriferidæ_ includes genera which are all characterised by a calcified spiral lamina for the support of the brachial appendages; and, however varied these may be, they always retain the distinctive characters of the group from their first appearance to their extinction. The Brachiopodist labours under the difficulties of not being able to determine what are the simplest, or which are the highest families into which either of the two great groups of his favourite class is divided; so far, then, he is unable to point out any evidence favouring progressive development in it. But, confining himself to species, he sees often before him great varietal changes, so much so as to make it difficult for him to define the species; and it leads him to the belief that such groups were not of independent origin, as was universally thought before Darwin published his great work on the _Origin of Species_. But in this respect the Brachiopoda reveal nothing more than other groups of the organic kingdoms. [Illustration: FIG. 60.—_Productus cora_ (D’Orbigny). Carboniferous.] “Now, although certain genera, such as _Terebratula_, _Rhynchonella_, _Crania_, and _Discina_, have enjoyed a very considerable geological existence, there are genera, such as _Stringocephalus_, _Uncites_, _Porambonites_, _Koninckina_, and several others, which made their appearance very suddenly and without any warning; after a while they disappeared in a similar abrupt manner, having enjoyed a comparatively short existence. They are all possessed of such marked and distinctive internal characters that we cannot trace between them and associated or synchronous genera any evidence of their being either modifications of one or the other, or of being the result of descent with modification. Therefore, although far from denying the possibility or probability of the correctness of the Darwinian theory, I could not conscientiously affirm that the Brachiopoda, as far as I am at present acquainted with them, would be of much service in proving it. The subject is worthy of the continued and serious attention of every well-informed man of science. The sublime Creator of the universe has bestowed on him a thinking mind; therefore all that can be discovered is legitimate. Science has this advantage, that it is continually on the advance, and is ever ready to correct its errors when fresh light or new discoveries make such necessary.” The late Joachim Barrande, the great palæontologist of Bohemia, bears similar testimony.