458 BUMPUS. [Vou. XII. 
(2) Is there true meristic variation ? 
Bateson (94, p. 102) states that “numerical change may be 
brought about in the series of vertebrae by two different proc- 
esses : first, by variation in the total number of segments com- 
prising the whole column, in which case the variation is truly 
meristic ; and, secondly, by variation in the number or ordinal 
position of the vertebrae comprised in one or more regions of 
the column, not necessarily involving change in the total num- 
ber of segments forming the whole series, and in this case the 
variation is homeeotic.’”’ He further states that though the 
latter form of variation may be associated with the former it 
is rarely possible in any particular case “to distinguish clearly 
whether such a change has occurred or not,’ because the 
terminal joints of the caudal vertebrze cannot be readily enu- 
merated. 
The application of the Rontgen rays often so clearly defines 
the centers of ossification of even the terminal caudal verte- 
bree that I have attempted to plot the several series on Plate C, 
though in a few cases, due to the imperfection of the specimens, 
tails in process of regeneration being quite frequent among the 
larger individuals, the number of the last few vertebrae have 
not been determined with certainty. Such specimens, five in 
number, are designated with ? over the est¢mated terminal 
joint. 
An examination of the plotted curve of the vertebral columns 
on Plate C will reveal an extremely irregular line passing from 
Specimen 1, with 45 vertebra, to 2 with 44, 3 with 47, etc. 
(Plate B, Specs. 1 and 2). There is, then, considerable mer- 
istic variation, and the second of the questions considered in 
this section is answered in the affirmative. Since it is pos- 
sible to enumerate the caudal vertebrz, we are in a position 
to answer the third question, vzz.: 
(3) Is homeeotic associated with meristic variation ? 
On Plate C the dotted ordinates indicate the specimens 
which are homeeotic, and, taking the specimens in blocks of 
twenty, let us see if the homceotic specimens of each block 
have a greater variation in the number of vertebrz than do the 
normal specimens. 
