MR. ST. GEORGE MIVART ON THE VERTEBRATE SKELETON. | 371 
that, if they cannot be deemed to supply what has been felt as a desideratum, they may 
yet provoke such investigation and criticism as by their refutation to elicit truth, and 
thus occasion, indirectly, what they may fail directly to accomplish. 
In studying these tailed Batrachians I have been especially perplexed as to how it may 
be best to regard the hyobranchial apparatus on the one hand, and the subcaudal arches 
and processes on the other. | 
This perplexity has resulted in an endeavour to obtain, if possible, satisfactory answers 
to the following questions. 
1. What is the best way to seek à priori a general view of the axial skeleton, or in 
what way may the axial skeleton as a whole be most reasonably regarded à priori ? 
2. What is the essential nature of ribs, transverse processes, and sternum ? 
3. What is the essential nature of branchial arches, and in what relation do they stand 
to ribs ? 
4. What is the essential nature, as compared with branchial arches, of the hyoidean 
arch, mandible, and more anterior structures? 
5. What relation exists between “chevron bones"* and other parts of the vertebrate 
skeleton ? 
1. As to the best way in which the axial skeleton, as a whole, may be regarded à priori. 
osecuted, the more it becomes plain and evident that trust- 
worthy views cannot possibly be arrived at without the study of development. Of late 
years this truth has been more or less recognized and acted on by almost all who have 
investigated the nature of the vertebrate skeleton. The most reasonable way, then, to 
endeavour to understand the skeleton is to recur to its earliest embryonic condition. 
Dr. Cleland, in his interesting papert on ribs and transverse processes (read at the Meet- 
ing of the British Association at Cambridge, in October 1862), differs from most of his 
predecessors in declining to regard the skeletal structures which envelope the cerebro- 
spinal centres as primary elements corresponding to those which embrace the trunk 
below, but rather as secondary offshoots from the latter. He says, “But the lamine of 
the vertebrz are at right angles to the main direction of the dorsal plates and the layers 
of the embryo; and even as the elevations of blastema in which they are developed are 
processes from the middle layer of the embryo, so do the lamine diverge from the main 
circle of the skeleton ; and in that respect they are to be compared with the various pro- 
cesses directed outwards to the skin in fishes, and with the epicostal bones in birds" 1. 
Although I think many of the ideas put forth by Dr. Cleland in the paper quoted 
exceedingly valuable, nevertheless I cannot follow him in this view as to the subordinate 
timating the nature and im- 
and secondary character of the neural arch ; for though in es i in 
portance of structures as parts of a system we must carefully study their mode of origin, 
yet we must nevertheless consider fairly the outeome and the result of that process, in 
order to get the most complete general conception of that system as à whole. Now 
though “the cylinder which the cerebro-spinal axis forms ” may be “ the product of only 
ossicles so often found beneath the caudal vertebræ of 
The more morphology is pr 
* By “chevron bones” I mean those detached Y-shaped 
animals above the class of Fishes. plc 
t Nat. Hist. Review, 1863, vol. iii. p. 116. + Loc. cit. p. 125. kai 
