J. Playfair McMurrich 195 
ual digits but to a common tendon, a point which will be elucidated in 
the succeeding part of this paper. 
Independently of the decided difference in the views of Hisler and 
myself as to the homologue of this muscle in the amphibia, it seems to 
me that Eisler is wide of the mark in attempting to discover an indica- 
tion of its independent existence in the lower forms, as he does in the par- 
tial separation of the profundus II into two portions. Its independence 
from the mammalian profundus is too recent phylogenetically to war- 
rant a hope of an absolute identification of it in the amphibia. Its ‘sepa- 
ration occurs only within the mammalhan phylum and, indeed, only in 
certain of the more highly specialized members of that phylum. I can 
see no reason for supposing that the occurrence of the muscle in the dog 
and the hywena has any phylogenetic relation to its occurrence in man; 
it seems rather to have been developed, i. e. separated from the profundus 
independently in the two cases. 
The palmaris longus is a muscle which may well be regarded as typical 
of the mammalha, though its absence in the monotremes, that is to say 
its lack of separation from the flexor communis implies that its differen- 
tiation has occurred within the limits of the phylum. The available evi- 
dence seems to point to its having been the first separation from the com- 
mon flexor, and its distinetness from the other components’ does not seem 
to be equal in different forms. In other words it is doubtful if the mus- 
ele is an absolutely equivalent structure throughout the mammalian 
series, but this, as well as the question as to the nature of the palmar 
fascia to which it is attached, can be more satisfactorily discussed later. 
The sublimis, like the palmaris longus, has been differentiated from 
the flexor communis digitorum within the limits of the mammalian 
phylum and is not an equivalent muscle throughout the group, since it 
contains a greater portion of the flexor communis in man and the higher 
forms than it does in the lower. It is hardly necessary to remark that 
the identification of the sublimis with the flexor brevis digitorum (per- 
foratus) of the reptilia, which has so frequently been made, is incorrect. 
The comparison of the sublimis in different mammals must rest upon 
the recognition of its relations to Windle’s five portions of the flexor 
communis and these relations are as yet unknown in the majority of the 
mammalia. IJ shall, accordingly, first describe what I have found in the 
forms which I have studied, namely in the opossum, the cat, the mouse 
and man, and employ the table contained in Windle’s paper only after [ 
have established the probable line of differentiation. 
In a section through the upper part of the arm of an opossum (Fig. 5) 
the five portions of the flexor communis are clearly recognizable, the con- 
