PROGRESS IN BIOLOGICAL INQUIRIES, 1935 435 



Examination of tissnes in oysters from the upper part of tlie 

 river show them to be more flaccid and transparent than those from 

 the lower part; they have less meat and less shell per unit of total 

 weight, have a higher water content, and lower glycogen content. 



In order to obtain a satisfactory solution of the pollution problem 

 in the York River it will be necessary to have a complete picture 

 of physical, chemical, and biological conditions in the river at the 

 present time, and as much of an historical background as possible. 



For information concerning the past history of the oyster indus- 

 try in York River, the investigators are dependent upon the willing- 

 ness of oyster planters to state the changes, if any, in their yield 

 of oysters before and since the establishment of the pulp mill. Since 

 they have agreed to cooperate in this, it is hoped that these inval- 

 uable data will be available. 



In connection with the York River pollution investigation experi- 

 ments were conducted in the Washington laboratory to determine 

 the effect of the pollutant from the York River on the rate of propa- 

 gation of diatoms which comprise the food of oysters. Other experi- 

 ments are being carried out to determine the effect of various mineral 

 salts on the propagation of diatoms. Numerous experiments along 

 this line are under way. 



BIOLOGY OF THE QUAHOG {Venus mercenario) 



An investigation of the life cycle of the quahog clam was carried 

 on by V. L. Loosanoff at Milforcl, Conn., where specially constructed 

 tidal tanks permitted the physiological observations under conditions 

 very closely approaching those of the natural environment. During 

 the year, observations were made on the gonad development of the 

 clam and its feeding activity. 



Young clams, when only 0.6-0.7 cm long, collected on the clam 

 beds of Long Island Sound near IMilford, Conn., in October, were 

 found to possess distinctly bisexual gonads with very strong male 

 predominance. In the majority of cases fully ripe spermatozoa oc- 

 cupied the central part of the lumens, while small oocytes and 

 oogonia constitute the inner walls of the follicles. 



In the middle of the summer, when the water temperature reaches 

 the critical point, the ripe spermatozoa are discharged. Soon after- 

 ward two distinct types of individuals become distinguishable as 

 definite males and females. In the males a second period of sper- 

 matogenesis begins in the autumn and continues at a reduced rate 

 throughout the winter. In the spring, with the increase of water 

 temperature, rapid branching of gonacl follicles takes place simul- 

 taneously with increased rate of spermatogenesis. The gonads then 

 have the typical male character of the adult. Spawning follows 

 later in the summer, when the size of the shell has reached a length 

 of 3 cm or more. 



In those individuals destined to become females the lumens of 

 the follicles remain empty after the spermatozoa are discharged. 

 At the end of the initial male phase the gonad follicles remain 

 distended with only a thin layer of undifferentiated cells and small 

 oocytes along the inner walls. In many cases numerous phagocytes 

 invade the follicles and devour the degenerated male cells. Oo- 

 genesis begins in the early spring. In June and July the follicles 



