Wilder.] 336 [June 21, 



First: in respect to the number of phalanges , which may be increased 

 to 14 (index of Globiocephalus) or, more commonly, reduced to 2, 

 (as with all the digits of Pteropidee and the pollices and primi of 

 most species), or to 1 (as with the primus of Simia) ; but all these 

 dimerous or monomerous digits and dactyls are visible and functional, 

 and numerical composition alone is evidently insufficient to deter- 

 mine their right to be included with the rest. But there may be no 

 phalanges whatever, and merely the metacarpal or metatarsal bone ; 

 and the question may arise as to the propriety of including that in 

 the enumeration. 



Second: in respect to its external visibility. The pollex of Hyaana 

 (63, 2, 306), has a single minute phalanx, supported by an 

 equally miuute metacarpal; the Hyrax capensis offers a similar 

 structure ; these digits are monomerous, concealed, and apparently 

 mnctionless, and would not be enumerated in a new species by one 

 who confined himself to the external characters which are believed 

 by many to serve for generic and specific distinctions; yet, undoubt- 

 edly, an anatomical description of the species would mention the ex- 

 istence of five digits in both these animals, in contradistinction to a 

 new Tapirus, which presents only a rudimentary pollical metacar- 

 pal. Again, although the pollices might be concealed from the sight, 

 they might be felt under the skin, and another and distinct element 

 must be taken into account in framing our definition. 



Third: a digit or dactyle may be trimerous and visible, and yet, 

 to all appearance, functionless or atelic, such are the "dew-claws" 

 of many Artiodactyla , and the slender index and annularis of Hippa- 

 rion (63, 2, 309, and 63, 3, 825); they are supposed to prevent sink- 

 ing into soft soil, but there seems no reason why the Camelidse should 

 be wholly destitute of these organs, if this is their use with the typi- 

 cal Ruminants ; such are also the pollices of the Canidae and Felidae 

 which have little if any power of motion. 



The above are instances of what are generally called " rudimentary 

 organs," to which so much attention has lately been directed, and 

 respecting which such contradictory opinions are entertained; this is 

 not the place for a discussion of the general subject, but the above 

 remarks may indicate the special questions as to the definition of 

 digits and dactyls. 



Histological Composition. 



The morphical value of this attribute of organs is variously esti- 

 mated by different authors; Agassiz, in the second passage already 



