76 S. S. Buckman — Reply to Prof. Blake. 



by reducing the resistance to the passage of the water." It is no 

 answer to this contention to say that under totally diiferent con- 

 ditions water is driven off from the hydrate of sodium sulphate by 

 the application of heat. Prof. Blake might as well argue, it seems 

 to me, that marble could not have been formed under plutonic 

 conditions, because, at the surface of the earth, and under the 

 pressure of one atmosphere, the aiDplication of sufficient heat will 

 result in the carbon dioxide being driven away from calcium 

 carbonate. It does not require much chemical knowledge to know 

 that if you alter the conclitions you may expect to obtain different 

 results. 



VIII. — A Eeply to Prof. Blake's Comments on Inferior Oolite 



Ammonites.^ 



By S. S. Buckman, F G.S. 



PROF. BLAKE'S book is a valuable work of reference ; but the 

 criticisms appear to be both hurried and inaccurate. In the 

 notice of my Monogi-aph the title is incorrectly given : there ai'e 

 certain other clerical errors ; and some mistakes which a little more 

 investigation would have prevented. 



While placing his comments in brackets, it is unfortunate that 

 Prof. Blake has not found some means to distinguish between 

 remarks based upon the author's words, and statements of his own. 

 This is especially noticeable in the " critical digest " of Haugia, 

 where remarks, which appear as if they originated with Prof. Blake, 

 are reall}' my statements in another form. 



Some of Prof. Blake's principal comments invite reply. For the 

 sake of brevity I will place them in italics between inverted commas. 



"The meaning of species and genera . ... is of the most restricted 

 Tcind . . . their distinctions arbitrary." As to the species, the charge 

 does not seem to be sustained in the part reviewed ; for out of 

 twenty-seven species described I am only answerable for five. I 

 have also combined as one species forms which a German author 

 regarded as three ; and in other cases I appear not to have made 

 enough species to please my critic. 



The genera are restricted I own ; it is part of the plan of the 

 work. I regard spefies as various developmental gradations. I look 

 upon genera as groups of species in more or less direct genetic 

 connexion, possessing certain features in common. Since species 

 in direct genetic connexion — and therefore genera — arose one from 

 another by the accumulation of successive slight modifications trans- 

 mitted in accordance with the law of earlier inheritance, the 

 distinctions between species or genera in direct genetic connexion 

 must be arbitrary at certain points. I have always admitted this; 

 but between the homoplastic developments which result from the 

 operation of similar economic laws on the heterogeneous descendants 

 of a remote common ancestor, the distinctions are not really arbitrary, 



1 The Annals of British Geology, by J. F. Blake, M.A., F.G.S., p. 308, 1891. 



