Plate II. 



Fig-. 3. Tlie larg-e specimens are clams of " Artificial Set " 

 reared from August 14 to September 20, iu sand-box at house- 

 boat. Two smaller specimens : " Artificial Set " left from August 

 14 to September 20 iu the original box on shore, and covered with 

 wire gauze (page 43). 



Fig. 4. Clams of "Artificial Set" reared from August 14 to 

 October 15, in the sand-box at house-boat. The two specimens on 

 the upper row, and the left-hand one in the middle row, show the 

 lines of growth resulting from slightly filing the edge of the shell 

 on September 20 (page 44). 



