48 



ELIOT E. CLARK 



APR^ 15 



Figs. 1 to 8 Camera lucida drawings of blood-vessels in a section of the 

 dorsal fin expansion of the tail of a rana sylvatica larva, on April 15, 16, 17, 18, 

 20, May 12, 20 and 31. Length of larva April 15, 10.5 mm., May 31, 29 mm. 

 Arrows indicate direction of circulation. Relative rate of circulation indicated 

 as FAST, MOD., moderate, SLOW, NO C, no circulation. Corresponding ves- 

 sels are numbered. Vessels present in one drawing which have been retracted 

 in the next are cross-hatched. The positions formerly occupied by vessels 

 which have retracted are indicated by dotted lines. In figure 8, the vessels 

 which were present in figure 1 are stippled, enl. (1: 50). 



