44 U. S. BUREAU OF FISHERIES 



action. A month later a typical female reaction was fully established 

 Another sex reversed male had a fully developed muscular reaction 

 but the discharge of eggs continued through the cloaca, indicatino- 

 a dehciency m the mechanism which forces eg^s through the ^ill? 

 All sex reversed females reacted as true males. ^From these observa- 

 tions the conclusion is reached that the female reaction has developed 

 as a secondary adaptation which provides a mechanism for the dis- 

 persal of eggs through the water. The male reaction is regarded as 

 a primary sex reaction of the oyster. 



A hermaphroditic oyster found among a group of new oysters 

 tested during the summer had an atypical reaction possessing the 

 characteristics of both sexes. This oyster discharged both eggs and 

 sperm and was capable of self fertilization. 



Present observations which establish a sex reversal in adult oysters 

 occurring simultaneously in both sexes can be explained by assuming 

 that the changes of the fundamentally bisexual gonad' of Ostreu). 

 virginica are controlled by some hormonic system in which the de- 

 velopment of one sex or another is inhibited. " Whether these changes 

 are hereditary characters which occur only in a certain group of in- 

 dividuals remains to be demonstrated by further observations. Since 

 abnormal sex ratios have been observed in adult oysters grown on 

 natural bottoms, understanding of the factors controlling the change 

 of sex is of obvious practical significance to breeders and may be 

 valuable for the maintenance of spawning grounds. 



Accumulation and storage of iron. — The possibility of increasing 

 the iron content of oysters by keeping them in water to which iron 

 oxide was added was demonstrated in a series of experiments con- 

 ducted in the laboratory at Woods Hole and in tidal tanks at 

 Milford. In the latter place iron was added to sea water by sus- 

 pending several pounds of nails in bags. There was considerable 

 discoloration of the water due to the presence of suspended particles 

 of iron hydroxide, but there was no material increase in the amount 

 of iron in solution. In several instances upon the addition of iron 

 oxide the amount of iron in solution even decreased. The accumula- 

 tion of iron in the tissues of the oyster gradually increased, however, 

 rising during a 6-month period from about 150 mg to more than 

 1,000 mg of iron per kilo of dry meat. Histological analyses proved 

 that iron oxide particles are absorbed by the blood cells of the gills 

 and are carried away and stored in the mantle and in the anterior 

 part of the body. 



Efect of industrial pollution on respiration. — Suspecting that 

 phenol salts may be the toxic substances of pulp mill waste which 

 affect the oysters, a study was made of the effect of pure phenol on 

 respiration. Using the technique developed in previous years tho 

 oxygen consumption of the oyster was measured under normal condi- 

 tions and in water containing phenol in concentrations 1:20,000; 

 1 : 1,000 and 1 : 500. The results show no significant changes in the rate 

 of respiration in the presence of this substance. 



OYSTER CULTURAL STUDIES 



Prediction of spawning and setting in Long Island Sound. — The 

 development of methods for accurately predicting the time and inten- 

 sity of setting of oysters in Long Island Sound was one of the prin- 



