252 MR. F. J. BELL ON THE ECHINOIDEA. [Mar. 4, 



tion within the limits allowed by inheritance, and the development of 

 useful variations into fixed and definite differences. The only criteria 

 which we can apply to problems of this character seem to be the ob- 

 servation (1) of what obtains in allied forms, and (2) of what obtains 

 in forms living under somewhat similar conditions. The variations 

 which appear to occur in Metalia sternalis during growth, and the 

 varieties of Diadema setosum, are to be cited as supporting examples 

 of the first, as are the Calcispongiae of the second of these criteria. 

 The well-marked keel of some specimens of B. carinatus seems, then, 

 to be the combined result of variability and of littoral existence ; in 

 other words, the species carinatus is not a good one, its sole character, 

 the keel, not being a constant attribute of its organization, but a point 

 which has been seized upon by a descriptive naturalist unacquainted 

 from lack of material with both its history and its variations. 



It now remains to settle which of the numerous names given to 

 this species should be adopted. In commencing the systematic 

 study of the Echini I hojjed to find in the synonymy of Agassiz 

 sufficient evidence of care to enable future workers " to simplify 

 their work by getting rid, to a great extent at least, of the bete 

 noire of zoologists, and apply their time to better things." For 

 the British naturalist, unfortunately. Prof. Agassiz's method of 

 nomenclature prevents this desirable result ; nor does he, in his 

 reference to pre-Linnsean authors, preserve his consistency : his 

 « Chronological List,' for example, ascribes the name Brissus to 

 Aristotle, but his synonymy to Klein (1734), while Echinus falls to 

 the Greek naturalist and to Rondeletius (1554). This diflficulty 

 might, however, be pretty easily eliminated ; but the omission of 

 synonyms is a more serious matter in a work of such pretensions : 

 thus in the synonymy of B. unicolor we find a reference to B. ova- 

 i«s, Gmelin (17H8), but no reference to the preceding species in 

 Gmelin's list, which is B. unicolor itself, as is quite distinctly shown 

 by the reference of both Gmelin and Agassiz to pi. xxvi. of Klein's 

 • Dispositio Echinodermatum.' The date of the specific term unicolor 

 being then 1/88, what is the date of carinatusl Agassiz, in his 

 synonymy, ascribes it to Lamarck, and so places it in 1816 ; but a 

 second reference to Gmelin shows that he recognized this species, 

 his typographical error of 43 for 48 being corrected by his own re- 

 ference to p. 249 of Klein's (or rather Leske's) work, where the 

 variety is spoken of as late- carinatus. I propose, therefore, to re- 

 tain the name unicolor. 



Passino- from the question of the identity of the species B. umcolor 

 and B. carinatus, 1 come to the consideration of the forms Meoma 

 and Metalia, which are reckoned as subgenera of Brissus by Prof. 

 Alex. Agassiz. Under Meoma two species are included, one of 

 which is found on either side the Isthmus of Panama — M. ffrandts 

 and M. ventricosa. Whether a larger series than the Museum pos- 

 sesses at present will enable us to show the specific identity of these 

 forms I do not know. The coarser and more distant tuberculation of 

 M. grandis affords, as Agassiz has remarked, a ready mark of dis- 

 tinction ; and it seems, from a comparison of the arrangement of the 



