No. 2.] THE STUDY OF VARIATION. A75 
generally considered to be attributes of the female, and it is 
barely possible that this affectation by the male is only an 
expression in habit of a general condition of physical conser- 
vatism. 
SeEcTIon IX. 
Are there anatomical grounds for the theory of vertebral 
intercalation ? 
If we accept the theory that there is a fixed intimate inter- 
relation between the appendage, girdle, and some one support- 
ing vertebra ; that all are parts of one developing area, parts 
bound together by some intangible law of correlation, the 
occurrence of the XX vertebra as the support of the pelvic 
appendages can be explained only by the theory of vertebral 
intercalation of Albrecht and Baur. 
If I understand the theory correctly, it is the function of one 
particular vertebra— or where more than one vertebra enters 
into the formation of the sacrum, of certain particular vertebrae— 
to give attachment to the pelvic arch, and no matter what sec- 
ondary alterations may occur before or behind, this vertebra or 
these vertebrz will tenaciously hold to their prescribed and 
inherited function. 
After examining the descriptions of several examples of in- 
tercalation given by Baur, in an earlier number of this journal 
(91), I fail to see that they necessarily support his theory. 
In the first place, Albrecht and Fiirbringer are acknowledged 
to differ in their interpretation of the Belgian python, and the 
mention of vertebral and costal asymmetry in Pelamis and 
Cimoliasaurus does not render the intercalation theory more 
probable. 
The case of the gavial, described by Baur and considered by 
Parker to show “very conclusively that, in place of one verte- 
bra, two or parts of two may arise,” is equally inconclusive. 
Baur writes: “It is well known that the typical number of the 
pre-sacral vertebrz in the living Crocodilia is twenty-four; there 
are two sacrals; the first caudal is peculiar by being convex. 
In a specimen of Gavialis gangeticus I found twenty-five pre- 
sacral vertebrz. As in all living crocodiles, the first caudal 
