The Scott is J i Naturalist. 101 



superordinate; (b) contradictory opposites put in the form of an 

 alternative, as when we are told that a group is characterised by 

 '•leaves divided or entire," or by "flowers regular or irregular," 

 or by "stamens indefinite or definite," which is very much like 

 saying that the distinctive feature of men is " having beards or 

 being without them." 



And, indeed, a plausible objection may be raised against giving 

 alternatives as characters at all ; for, strictly speaking, no alterna- 

 tive can characterise. A fact is never an alternative — in other 

 words, a thing is what it is, a definite something with definite and 

 positive qualities ; and so long as it continues to be that thing, it 

 is not and cannot be anything else. Hence to say that a group 

 has flowers red or white or yellow, for instance, is so far not to 

 ascribe one positive attribute to its members, but to give us a 

 choice of several ; and so, in strictness, is not to characterise. 

 But then, on the other hand, if our alternatives be exhaustive, 

 there is no question that we do obtain from them some positive 

 information. Although we may not be able to say off hand what 

 the colour may be in the flower of any given member of the 

 group, it will always be something if we can with confidence affirm 

 that it will be one of a limited number, red or white or yellow, 

 and not blue or pink or green. Hence, in this sense — i.e., if we 

 can exhaust the alternatives at any particular stage — we may 

 enumerate them as a character ; but if we fail to exhaust them, or 

 if we deal in contradictory alternatives, we have no right to adduce 

 them as a character or to present them as part of the defining 



mark. 



[To be continued.) 



THE PERTHSHIRE NATURAL HISTORY MUSEUM. 

 By F. BUCHANAN WHITE, M.D., F.L.S. 



( Continued from page 53. ) 



As has been already stated, one and a half table-cases are devoted 

 to the zoological index collection. These cases contain thirty-six 

 trays, thus apportioned : — Protozoa, one tray ; Cozlenterata (includ- 

 ing Spongia), five trays ; Echinodermata, three trays ; Arthropoda 

 and Mollusca, each six trays ; and Vertebrata, twelve trays. 



The Protozoa are illustrated by drawings of selected types of 

 the species that have no shell, and by models (obtained from 

 Fritsch of Prague), of the Foraminifera and Radiolaria, as well as 

 by specimens of the actual shells of the latter groups. 



