320 The American Naturalist. [April, 
intercentra, and do not necessarily pertain to them; third, that in cer- 
tain Lacertilia (e. g, Anguis) the chevron bones are coéssified with the 
centra, as is the case in the Batrachia Urodela; fourth, that the neural 
arches of the caudal vertebre of Lacerta are partially divided on 
on each side by a fissure or foramen, which he regards as evidence that 
the vertebre of reptiles consist of two original elements, that is, are 
produced by the fusion of the two bodies of the embolomerous type of 
column. His general conclusions are stated at the end of the paper as 
follows: 
“ (1). The construction of complete vertebre with bodies and arches 
in the series of the A miidæ, as in that of the Stegocephali and all liv- 
ing digitates begins in an embolomerous form, i. e., with double verte- 
bree to each segment. (2). The change of these double vertebrze into 
simple ones is accomplished by the fusion of the pairs after both verte- 
bre more or less, or especially the posterior one, have retrograded. 
(3). The rhachitomous vertebra is neither a primitive nor an indepen- 
dent appearance, but only a transitional stage in this change. (4). 
The principal significance of the embolomerous origin of the vertebra 
for the digitate vertebrates lies in the inheritance of certain remains of 
the double structure, the arches, transverse processes and ribs whose 
permanent forms are only to be understood on this ground.” 
As regards the question of the non-homology of the vertebral bodies, 
I belieye that I have shown that they are for the most part not homol- 
ogous as between the Anamnia and the Amniota, but that the homol- 
ogy of the contents of each of these divisions is shown by paleontologic 
evidence. Itis also clear that many if not all of the vertebral bodies in 
the two great divisions in question must be homologous,otherwise we must 
have as many original ancestors of the vertebrata as there may be kinds 
of vertebral centra, a proposition which no one will be found to believe. 
In fact the embryology of forms of life of comparatively recent origin 
such as the Lacertilia, is apparently, from Göttes researches, as it should 
be supposed a priori, incompetent to explain the phylogeny of structures 
which received their definite completion in the paleozoic ages of time. 
Owing to cenogeny, is is quite certain that structures may be directly 
related phylogenetically, which may appear to be in their present on- 
togeny not homologous. This consideration applies to the supposed 
non-relation of the chevron bones to intercentra. This relation is uni- 
versally demonstrated by paleontology, and better evidence than the 
changes of position in late forms such as occurs in Anguis (to which I 
have added Anniella) and the snakes, must be cited to invalidate it. 
