CONTENTS 
Variation in the maximum depth at which fish can live during summer in a mod- 
erately DEEP lake with A THERMOCLiNE. By Frank Smith. (Document No. Page 
970, issued September 15, 1924.) 1-7 
Black tumor of the catfish. By Raymond C. Osburn. (Document No. 972, issued 
March 24, 1925.) 9-13 
Growth and degree of maturity of chinook salmon in the ocean. By Willis H. 
Rich. (Document No. 974, issued March 24, 1925.) 15-90 
Seasonal distribution of the plankton of the Woods Hole region. By Charles J. 
Fish. (Document No. 975, issued April 2, 1925.) 91-179 
Digestive enzymes in poikilothermal vertebrates. An investigation of enzymes 
IN fishes, with comparative studies on those of amphibians, reptiles, and 
mammals. By Walter A. Kenyon. (Document No. 977, issued April 2, 1925.) 181-200 
Growth and age at maturity of the Pacific razor clam, Siliqua patula (Dixon). 
By F. W. Weymouth, H. C. McMillin, and H. B. Holmes. (Document No. 984, 
issued July 23, 1925.) 201-236 
Fishes of the republic of El Salvador, Central America. By Samuel F. Hilde- 
brand. (Document No. 985, issued August 28, 1925.) 237-287 
Fur-seal industry of the Commander Islands, 1897 to 1922. By Leonhard Stejne- 
ger. (Document No. 986, issued October 2, 1925.) 289-332 
General index 333-347 
HI 
