No. 2.] THE STUDY OF VARIATION. 469 
of specimens should present homeeotic variation than was the 
case with the three just mentioned, belonging to the abscissa 
of 35%. A reference to the plate will show that a less number, 
only fifteen specimens (46%), have homeeotic sacra. 
A still smaller number of homeceotic specimens should be 
found on the abscissa of 35%, and, in fact, of the forty-four 
specimens arranged on this line but thirteen present cases of 
forward homeeosis, 29%. 
An even greater diminution in the number of homceotic 
specimens should be found on the abscissa of 32%, where we 
count fourteen specimens, only two of which, barely 14%, are 
homeeotic. 
On the abscissa of 31% among four examples there is only 
one that is homeeotic, and among three examples on abscissa 
of 30% there is also only a single homeeotic individual. 
There are thirty-five specimens below the mean abscissa of 
33% and twenty-one specimens above. The former exhibit 
eighteen cases of forward homeeosis, 2.¢., 51% are homceotic ; 
the latter exhibit only four, z.¢., 19%. 
This effort to prove that the sacral ribs are developed as the 
result of centripetal influence bears directly upon the proposi- 
tion of Bateson “ that individuality should not be attributed to 
members of a series which has normally a definite number of 
such members,” for it is shown that the normal XIX verte- 
bra owes its specialized form to the molding influence of sur- 
rounding parts, and not to some inherited directive influence 
upon one particular vertebra. It shows that a “redistribution 
of differentiation’ may and frequently does take place. 
The appearance of the appendage at a definite topographical 
point, without respect to the location of certain segments of 
the neighboring axial area, is in harmony with the view of Pro- 
fessor Whitman ('93) that the real unity, both in development 
and in adult stages, is the organism as a whole, “that the 
organism dominates cell formation.” 
The view here advanced also receives direct support from the 
facts of embryology, as shown by the following extract from 
Weidersheim’s ‘“Grundriss” ('93): ‘Mit anderen Worten — 
und ganz dieselben Gesichtspunkte ergeben sich auch fiir 
