506 DR. C. I. FOESYTH MAJOR ON 



Netscheri (PI. 38. fig. 23, ^x-) ; in Onjctolagus crassicaudatus (fig. 22, pc), where it 

 seems on its way to undergo a synostosis with Metat. II ; in Caprolagiis hispidus 

 (fig. 2^,p>c), where it has shifted its position completely to the volar side of Metat. II ; 

 in a specimen of Sylvilagus brasiliensis, from the C o^oen ha gen Museum ; and lastly in 

 the Wild Rahhit, where the ossicle is very small and situated volad as in C. hispidus. 

 I owe this specimen to Mr. Sherrin, Articulator in the Nat. Hist. Mus., who at my 

 request dissected some Hahbits' feet, in search of the ossicle in question. 



In his careful researches " Ueher den Siiugetier-Pra^hallux " *, Tornier met with this 

 ossicle in one case only of all the Rabhits' and Hares' feet examined, and great stress is 

 laid on this isolated occurrence. " Die Lage dieses iiberziihligen Knochelchens beweist 

 imwiderleglich, dass es selbst homolog ist dem Knochen welcher bei vielen der liisher 

 untersuchten Tiere der t 1-Medialseite gegeniiber liegt. Da er an Hasenfiissen 

 individuell auftritt und an jungen Kaninchen- und Hasenfiissen nicht vorhanden ist, so 

 ist es zweifellos, dass er eine secundiire Bildung ist, und daraus ist mit Sicherheit zii 

 schliessen, dass er audi bei den Tieren, wo er iramer vorkommt, eine seouudare Bildung 

 ist " t. And again : " Der muse, hallucis abductor-Knochen kommt endlieh dritteus 

 zuw^eilen bei erw^achsenen Vertretern solcher Thierarten vor, bei welchen der Knochen 

 unter norraalen Umstanden weder im Alter noch wahrend der Ontogenese vorlianden ist 

 {Lepus timidus) | ; bei diesen Individuen ist er — dagegen giebt es keinen Widerspruch — ■ 

 secixndiir entstanden" i^. Therefore, as already stated in the first-quoted passage, he 

 again asserts that the homologous boue in all other Mammals is equally secondary. 



Even if the presence of the ossicle in question, as believed by Tornier, w^ere limited to 

 exceptional cases in one species of Lepms, the author's arguments w^ould not be 

 valid. It is one of the characteristics of these reduced " accessory " bones to ossify 

 very late (Thilenius) ; and its exceptional appearance in L. europccus could, a prion, 

 be interpreted quite as well in the sense of a disappearing element as in Tornier's 

 sense. But the presence of this bone as a constant element in Lagomyida3 and several 

 Leporidae totally changes the aspect of the question. In the more primitive forms of 

 La"-omor})ha, the ossicle seems always to be present and pi'oclaims itself a reduced 

 element by its varying size and position. In those Lepoi'ida: — of which L. europceus is 

 the prototype — which are the most specialized for leaping, we must expect it to be of 

 quite exceptional occurrence. 



The ossicle has been observed in the " Hare" likewise by Pfitzner ||, who calls it the 

 pnecimciforme. As to whether this and similar accessory bones are to be considered 

 as "secondary" or "sesamoids," Pfitzner has shown us the way how to proceed^, 

 viz. that we cannot base our conclusions on the examination of a single specimen 

 or a few species. The " pryecuneiforme " has been studied by Pfitzner especially 



* G. Tornier, " Ueber deaSaugetier-Pniihallux. Eia dritter lii'itrag zur I'liylogciicse dcs iSaugoticrfusses." Arcb. 

 f. Naturgcsch. 1S91, pp. 115-:i04. 



t Op. cil. p. 1^1. + Meaning Lejtus eurupieiis, Pall. § Op. cit. p. 190. 



II Moiph. Arb. (Soliwalbe) i. p. 533 (1S92) ; iv. p. 354 (189.5). Prof. Pfitzner lias kindly informed me that the 

 species is L. eufop)(^vs. Pall. 



f LI. CT. ; and Morph. Arb. vi. p. 394 (1S96). 



