278 



BULLETIN: MUSEUM OF COMPARATIVE ZOOLOGY. 



the trapezoid, on the contrary, is small and laterally compressed, as is 

 also the proximal end of metacar^ml li. 



The tendons of the muscles and the nerve of digit i bifurcate (Fig. Q, 1). 



This intermediate stage leads up to conditions in which there are two 

 complete and entirely distinct digits. The duplication may extend even 



n. m. 



II. 



i:.....i6. 



Fig. Q. — Posterior view of left polydactj'le manus, showing innervation, i", i'', 

 supernumerary digits; 1, first branch of median nerve, which bifurcates twice, the branches 

 from the second bifurcation going to digits i" and i^ I \iatural size. 



to the carpus, and the two digits thus formed may be nearly as large as 

 the functional digits (in and iv) of the manus. Six such cases were 

 examined. In the typical condition (Plate 13, Fig. 21) the supernu- 

 merary digits (i", 1*) are somewhat smaller than in and iv. Each 



