60 PROF. G. B. HOWES AND MR. H. H. SWINNERTON ON THE 
The Long Bones.—Under this head we include the humerus and femur, radius and 
tibia, ulna and fibula. They have all been so often described, from Giinther to 
Osawa, that detailed recognition by us would be superfluous. We would only add that 
the condylar foramina of the humerus, originally observed by Dollo (84), are both 
fully formed at Stage Q (PI. VI. fig. 10, fren., fec.), and that the inner has from the 
first period of differentiation its canal-like character. 
The long bones are the first of all the cartilage-bones to ossify. 
Carpus and Tarsus, with Phalanges. 
It is evident, from the study of both carpus and tarsus, that chondrification sets in 
correspondingly (for the tarsus, cf. Pl. VI. fig. 15). One inexplicable feature is the 
long duration of the cartilaginous state of both. Ossification begins in both post- 
axially (as is seen in fig. 14 for the carpus), but not until the rest of the limb is fully 
ossified. 
We have examined both carpus and tarsus at all stages of development back to Q, 
where these elements are first chondrified. ‘To make sure of detail, we have employed, 
beyond clarified dissections, serial sections cut horizontally. 
The Carpus.—Giimther described ten carpal elements, and in this he has been 
followed by others. He appears to have missed one of the centralia, and to have 
confused the other with the proximal elements, which he describes as five in number 
(67. p. 612). Osawa, the latest writer on the subject, correctly records eleven 
elements (98%. p. 528), the eleventh being the secend centrale, detected by Bayer 
(84. p. 237), who first applied to the parts a rational terminology. It was, however, 
independently discovered by Dollo and Baur (86*. p. 188), the latter opposing Bayer’s 
conclusion that its supposed absence is due either to disappearance or union with 
another carpalelement. In this he was right, for we find it always present. 
None of the afore-mentioned observers describe the precise size and relationships 
of the two centralia to each other and the adjacent carpal elements. Osawa, however, 
gives a very different delineation to the dorsal and ventral aspects of the same pair, 
and figures the preaxial as outwardly extended between the radiale and first carpale as 
seen from the dorsal surface (98°. p. 527, figs. 13 & 14). While we can confirm the 
accuracy of this, we are able to record further suggestive details. From a comparison 
of our figs. 12 and 13 (Pl. VI.) which represent the opposite carpales of the same 
individual, we find that the right (fig. 12) is normal but that the left (fig. 13) is 
exceptional, in the fact that the preaxial centrale (pr.c.) is smaller than the postaxial 
(po.c.) and lies wholly between the radiale and the first carpale, instead of merely ex- 
tending between them. ‘The postaxial centrale, on the other hand, is correspondingly 
enlarged, whereby it articulates with the second carpale, as well as with the third and 
fourth, to which alone it is usually related. There is thus to be observed an inverse 
