CHANGES FOR ADAPTATION IN THE MOLE 347 
protrude beyond the fur to interfere with movements, but are 
long enough to function as touch organs. Finally, the very 
degenerate condition of the eye shows a remarkable degree of 
adaptation, corresponding very closely with that of other animals 
whose entire lives are spent in darkness (EKigenmann, ’09). 
Even though the receptor senses and external changes show 
marked deviation from the mammalian type, the most noticeable 
changes are in certain portions of the skeleton and the muscles 
which control these parts. These are most conspicuous in the 
pectoral and pelvic regions. These modifications which are 
especially adapted to the environment will now be described in 
detail. 
In order to adapt the mole to the fossorial life which it leads, 
the skeleton has been greatly modified. Since the animal’s 
chief employment consists in digging, its main strength is con- 
centrated in the fore-quarters where the bones and muscles 
are developed to a marvelous extent. Plate 1 shows the enor- 
mous development of the bones of the pectoral region as con- 
trasted with that of the pelvic. The whole pectoral girdle is 
pushed forward close to the base of the skull, giving the animal the 
appearance of having no neck. ‘This forward displacement of the 
girdle is due to the great development of the manubrium or pre- 
sternum (Pst). To compensate for this the scapula (S) has 
grown backward so far that its posterior end lies in about the 
normal position found in most mammals. 
The sterna of the moles apparently vary with different species. 
According to Owen (’66) and Flower (’85) in Talpa europaea, it 
consists of six or seven parts; the manubrium or presternum, the 
mesosternum, consisting of four (Owen) or five (Flower) sterne- 
brae, and the xiphisternum. In the individuals of the species 
under observation I have found the mesosternum consisting of 
but three bones, the posterior two or three of Talpa have evidently 
coalesced to form one in Scalops and Scapanus (fig. 16). 
The total length of the sternum is 36.4 mm., of which the pre- 
sternum forms almost half. The length of the different por- 
tions is as follows: presternum 17.7 mm.; mesosternum, 12.4 mm., 
the first joint being 3.8 mm., the second joint, 3 mm., the third 
joint, 5.6 mm.; xiphisternum, 6 mm. 
