376 U. S. BUREAU OF FISHERIES 



tion is still more amazing. Active spermatozoa are present in every 

 month of the year. Upon being placed in the water they swim ac- 

 tively and behave in normal fashion. One interesting observation 

 has been made on the movements of spermatozoa. Durmg the study 

 of fertilization it has been observed that sperms of different clams do 

 not behave similarly. While they all exhibit spiral movements, 

 the spermatozoa of about 75 percent of males move in circles in an 

 anti-clockwise direction, while the other 25 percent of the males pro- 

 duce sperms moving in the opposite direction. The sperms of one 

 male usually all move in the same direction. On several occasions 

 young ovocytes were found present in adult males 6 to 8 years old. 

 This apparently shows the potentiality for change of sex even in 

 adult clams. However, gonads of truly bisexual character in an 

 adult clam have been observed in one case only. Functional her- 

 maphroditism has been observed only once. 



A study of the spawning of clams and its physiology was con- 

 ducted last summer. It has been found that it is very difficult to 

 induce the spawning of clams, especially females, under the labora- 

 tory conditions. The critical spawning temperature is higher than 

 that required for the oyster. Under the laboratory condition 25° C. 

 was the minimum spawning temperature. 



To study the growth of young clams three experimental beds rep- 

 resenting different environmental conditions were established in 

 different parts of Milford Harbor. Young clams from all of the 

 beds were measured at regular intervals and the progress in growth 

 recorded. 



The feeding of clams depends upon the combined action of syphon, 

 gill epithelium, and adductor muscles. At present only shell move- 

 ments are being studied. The clams are kept under natural condi- 

 tions in the large concrete tanks, 20 by 18 by 6 feet, in which the 

 water is renewed by tidal action twice each day. Since the beginning 

 of the experiment on October 17, 1934, over 160 records of shell 

 movement have been obtained covering the range of temperature 

 from 0° C. to 13° C. 



A study of the glycogen content of hard-shell clams was begun 

 last March. Samples of clams were collected every 2 weeks and the 

 meats analyzed. The glycogen content varies greatly with physi- 

 ological changes occurring in the clams at different seasons of the 

 year. The maximum quantities of glycogen found in clams during 

 the prespawning period constituted 10 to 11 percent of the meat 

 weight (fresh basis). After spawning a very sharp drop takes 

 place until at times it equals only 3.3 percent of the meat weight. 

 Gradual recovery takes place after that and during the winter the 

 glycogen content of the clams constitutes 6 to 9 percent of total 

 weight. Grown under similar conditions clams always have a higher 

 glycogen content than the oysters. 



REHABILITATION OF PUBLIC OYSTER BEDS IN NORTH CAROLINA 



In order to restock the depleted natural oyster beds of North Caro- 

 lina, extensive operations for the transplantation of seed oysters 

 have been carried out under the direction of Dr. H. F. Prjrtherch, 



