256 BULLETIN: MUSEUM OF COMPARATIVE ZOOLOGY. 
(93) figures a single case in which the hallux was developed and 
duplicated. 
In both the cat and dog the normal manus is composed of five 
digits, but the pollex is much reduced in size. In the pes only four 
functional digits are present, the hallux being represented by merely a 
rudiment of metacarpal 1. These animals are therefore tetradactyle in 
the pes, andit is there only that we may look for evidence of reversion, 
unless we assume the existence of a hexadaétyle ancestor. 
Most of the digital abnormalities in Carnivora occur on the radial 
side of the manus or pes; digits 1I-v remain practically normal in all 
cases. This is an important fact when the polydactyle conditions in 
other animals are considered, for it shows that the digits which vary are 
in most cases those which have been either reduced or modified in the 
course of phylogenetic development. 
In the pes of the cat the digital abnormalities fall into three classes : 
(1) Five digits, each possessing three phalanges (Fig. B). 
(2) Six digits, five of them possessing three phalanges each, the sixth, 
which resembles a normal pollex (Fig. C), exhibiting only two. 
(3) Six digits, each having three phalanges. This is the condition of 
most frequent occurrence ; the digits in this case are usually so formed 
that the pes is bilaterally symmetrical. Bateson lays considerable stress 
upon this symmetrical condition, which is brought about in the following 
manner. The distal phalanges of the normal extremities are retractile, 
and are always drawn back to the ulnar side of the second phalanx (that 
is, in the right extremity to the right, and in the left to the left). For this 
retraction the second phalanx of each digit is hollowed out on the ulnar 
side. The supernumerary digits, however, do not conform to this plan, 
but their ungual phalanges are drawn back to the other (radial) side of 
the manus or pes; consequently the second phalanx is hollowed out on 
the radial side to correspond. This change in the symmetry of the 
phalanges may extend also to the second digit (11). 
In the manus of the cat we find the same three types of poly- 
dactylism and in addition a fourth type, in which there are seven digits 
present. Digits u-v are always normal; on the radial side of 11 are 
three extra digits, the most radial of which is amorphous (Bateson, 
"94, Fig. 86, p. 319). Torrey (02) describes a similar case.in which 
seven digits appeared, but the most radial was resorbed soon after birth. 
In the case described by Howe (:02) three complete extra digits were 
developed, which he considers similar in structure to digits 1, Iv, and Vv. 
To this class belong the majority of polydactyle cats. When six meta- 
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