504 DR. C. I. FOESYTH MAJOR ON 



adaptation to a new function does not in any way explain the typical features of their 

 limbs. " Where we meet with similar adaptations, the original condition has never been 

 completely effaced " (italics mine) *. 



The undivided condition of the " hamatum " in terrestrial Mammalia can now be 

 explained in a very simple and obvious manner, since by means of the " os vesalianum " 

 we are enabled to sliow that the presence of a separate carpale 5 is not in the least 

 limited to af evv cases among Cetacea, but is a frequent occurrence in other Mammalia 

 likewise, a circumstance which has hitherto either been wrongly interpreted or entirely 

 overlooked. Tlie " hamatum " of Mammalia is not carpale 4 + 5 of Reptilia, but it is a 

 carpale 4 which, as a rule, has become enlarged, and has, in addition to its own functions, 

 usurped those of carpale 5. Whether a usurjDation is in ecery instance to be assumed 

 is another question, which cannot be entered into here ; it may, for the present, be 

 sufficient to repeat that the suj^eradded function of carpale 4 may often be not the 

 cause but the consequence of the degradation of carpale 5. 



Where carpale 5 is absent in the terrestrial Mammalia, it has, so far as my experience 

 goes, either disappeared by atrophy, or become absorbed by the tuberosity of Metac. V, 

 as in Man. Finally, therefore, since the fusion of carpale 5 with carpale 4 has never 

 been observed in these, its occurrence may be peculiar to the Cetacea. 



Hem ARKS ON the Metatarsus and Tarsus of LAGOMORrflous Eodentia. 

 1. Motatarsale I and Tarsale 1. — Krause states f that in adult E.abbits the os tarsale 1 

 becomes fused with the os Metatarsi I, and for this he refers to his text-tigure 6i B. 

 He continues as follows: — "In new-born animals, however (fig. 64a), the tibial 

 prominence of the proximal extremity of Metat. I is independent, and consists of an os 

 tarsale and a lengthened distally-pointed bone, representing a rudiment of the hallux, 

 at tlie distal end of M'hich there is inserted the tendon of the m. tibialis anticus. In 

 reality, therefore, the os tarsale 1 of the Rabbit is the o.t. 2 of Man, and the os 

 Metatarsi I of the Rabbit represents the os tarsale 1. the hallux and os Metat. II of 

 Man." So far as the fig. 64 a, " horizontal section of right hallux of a 12-days-old 

 Rabbit." goes, this is correct, assuming that the two outline-figures of the tarsalia 

 (1 and 2) are meant to show them in a cartilaginous condition. But the lettering of 

 fig. 64 b, " right os Metat. I " (meaning Metat. II of comparative anatomists) of an adult 



* " . . . muss daran festgehaltou wcrden, dass die Anpassuiig au eine neue Fuiictiou keiueswtgs das Typische der 

 Gliedmaasseni'orm zu erklaren vermag. Wo wir .solchen Anpassuiigen begeguen, hat sich der urspriingliche Zustand 

 nie ganz verwischt. In der Flosse der Baiaenen ist das Saiigcthierarmskclet klar zu erkennen, ebeuso wie bei den 

 Cheloiiiern die Schildkroteuextremitiit. Hier bei den Fiialiosaiiriern ist aiieli gar niehts auf Reptilien Beziehbares 

 am Flossenskelet vorhauden. Von der schoii bei Amphibieu vorhandeiien Hifi'erenzirung vou beiderlei Giiedmaassen 

 iiicht ein blasser Schein ! Es miisste also an der Gliedmaasse ciii RUckgang bis zu den erstcn Aufangen erfolgt 

 und von diesen her cine selbstandige .\usbildung eingetretcn sein, wenu Reziehungen zum Reptilientypus hier 

 einmal an der Gliedmaasse bestandeu haben mogeu. JedeiiCalls gehiireu diese Bildungen nielit in die Reihe der 

 Reptiliengliedmaassen, soudern unter die Anfiiiige, wie sie denii gerade in dem schou bercgten Mangel des Different- 

 werdens von Vorder- und Hinterextremitiit sogar unterhalb der bis jetzt bekanntcn Reptilien sich stellen. So 

 birgt sieh iu diesen Fragen ein interessantes Prjblem." ( Vergl. Anat. der Wirbelthiere, p. 531.) 



t W. Krause, Anatomie d. Kauiuchens, :^"' Aufl , p. l;i2 (lKS4). 



