OF THE TO.NGLKS OF THE MAMMALIA. 763 



not been found in any otlier ton,2;ue there is insufficient luaterial 

 in wliich to work out its phylo.i^enetic significance. 



Tlie Suhliiigaa. — Tlie various Lemuroidea are difterentiated 

 from one another by the shape, mobility, and characters of the 

 crests and denticles as follows : — 



1. Sublingua triangular or lyrate, has tlu-ee ventral crests, 

 and is veiy mobile. The apex is divided into a brushwork of 

 denticles : — Lemur, IIa2)aU)aur, Indrisidee. 



2. Sublingua a large tlat plate adherent to the under surface 

 of the tongue by its central parts ; no denticles present, but a 

 strong keel-like ridge on its under surface projects forwards in 

 the middle line : — Chlromys. 



3. Sublingua large, tongue-shaped, but not quite so free as that 

 of Lemur. There is only one median ventral crest, but the 

 dorsal surface has a crest of variable prominence. This crest, the 

 characters of the denticles, and the variations in the consistence 

 of various parts of the sublingua are important : — 



Tn Microcehtts the sublingua is uniformly thick, the median 

 dorsal crest is slight, and the denticles are moderately long. 



In Nycticebus and Loris the central parts of the sublingua are 

 thicker than the lateral parts, the median dorsal crest is small 

 and the denticles are of moderate length ; they are discrete in 

 the former and close in the latter, but there is no essential 

 difierence between the sublinguse of these genera. 



In Perodicticus the median ventral crest is bifurcated pos- 

 teriorly, the median dorsal crest is very prominent, and the 

 denticles are long aiid slender. 



In MicrocshiLS, Crcdago, and Hemigalago the anterior border of 

 the sublingua is broad, Init in Loris and JSfycticehiis it is more or 

 less pointed. 



The Plicce Flmbriatce of the Simiidfe are derived from the sub- 

 lingua by a process of phylogenetic reduction, and I showed that 

 the plicae of Anthropopithecus troglodytes with the intervening- 

 piece of mucosa form a soft triangular field resembling a sub- 

 lingua ; this is even more marked in the tongue of the new-born 

 child, as described and figured by Gegenbaur. The plicae of 

 Phascolarctos cinereus, however, do not bound such an area. 



The tongue? of the Gibbons, CercopithecidaB, Cjebidae, and 

 HapalidfB illustrate the ultimate stage of reduction, for no traces 

 of the sublingua. or plica are present as a rule in the extra-uterine 

 vstage. In the fcetal Gibbon, as shown by Deniker, there is a 

 well-marked sublingua; and I observed two minute plicae in a 

 young Cercopithecus patas, so it is probable that the foetuses of all 

 Primates have sublingute. 



If one examines a sei-ies of human tongues at diffei-ent ages, 

 one finds that the new-born child has well- developed plicfe or an 

 actual sublingua provided with taste-buds. As age advances the 

 buds disappear and the plicae diminish in size. These taste-buds 

 probably account for the more acute sense of taste in the child. 

 Experimental Uiethods also demonstrate that the sense of taste 



