84 BULLETIN : MUSEUM OF COMPARATIVE ZOOLOGY. 
described by Bourne ('84, p. 86), Benham (’94, p. 477), Adolphi (96, 
p. 133), and others. But such masses may, in my opinion, better be 
interpreted as ankylosis, symmetrical if the line of fusion be transverse 
to the axis of the column, or unsymmetrical if the line of fusion has been 
oblique. This is borne out by the fact that near, though not necessarily 
contiguous to such an unsymmetrical mass, there is usually found a comple- 
mentary mass (see Benham, ’94, pp. 477, 478) ; i. e. if by oblique fusion 
we have a mass containing one right half-vertebra and two left halves, 
we shall find near by another mass representing one left half-vertebra, 
and two right halves. The vertebrae: lying between these two masses 
will be morphologically oblique, their two halves in each case belonging 
to different somites, although the adjustment of growth may have 
brought these to an apparently normal position, with transverse axis at 
right angles to the main axis of the column. That the right and left 
halves of a vertebra may slide upon each other, is held by Adolphi 
(96, p. 136) to be confirmed by embryological evidence. Such unsym- 
metrical masses have not been accompanied by correlative asymmetry 
in musculature and nerves where the soft parts have been described. 
Symmetrical fusion of vertebrae has been described by Howes (93, 
p- 295), Adolphi (95, p. 466, and ’96, p. 122), and others. An actual 
increase in number of vertebrae, and also an indicated increase by groov- 
ing and partial splitting of vertebra, and by bifurcation of transverse 
processes, have been noticed by Bourne (’84, p. 87), Benham (94, p. 478), 
and others. The cases of actual increase described were in Anura, and 
resulted from separation of the anterior portion of the urostyle as a 
supernumerary vertebra, Adolphi (95 and ’96) has recorded forty-three 
cases of vertebral fusion in Bufo, Pelobates, and Rana, and has deter- 
mined the nerve relations. He finds that in such cases of fusion the 
spinal nerves are not suppressed, but emerge through foramina in the 
fused mass; they are, however, liable to be weaker than normal. 
Such supposed direct evidence of intercalation and excalation is capa- 
ble of being interpreted as pathological, rather than as a disturbance 
tending primarily to alter the serial number of metameres, — especially 
since it is almost entirely confined to the skeleton, without involving 
musculature or nerves beyond the narrow limits necessitated by local 
accommodation to the distorted vertebra. No evidence of the inherit- 
ance of such abnormalities has yet been offered. Such would be valu- 
able as determining whether or not these variations show persistence. 
Tf so, it would indicate that they are sports; if not. the pathological 
interpretation would be strengthened. 
