130 BULLETIN OF THE 
this latter change being a secondary step, which is preceded by the 
proliferation of the somatopleure and the formation of the pectoral 
plate, as already described. This difference should be noted, that in 
the Salmon, according to Ziegler's (87, p. 619) account, the lateral 
ectodermal fold extends from the pectoral region to that of the anus, 
whereas in the case of Fundulus no such fold of the ectoderm is 
found. 
I have examined both the Cod and the Shad, in which Ryder affirms 
that the ectodermal fold is the earliest trace of the pectoral fin, and find 
that these forms agree with Fundulus to the extent at least that the 
proliferation of the somatopleure in the pectoral region precedes any 
specialization or modification in the ectoderm. I cannot account for 
this difference in our results, unless my supposition, that Ryder’s studies 
were made chiefly without the aid of sections, is correct. 
Cuicaco, January, 1892. 
