PROGRESS IN BIOLOGICAL, INQUIRIES, 193 3 355 



iii<j: niicroor^anisnis have boon isolated and their cultiiros are being 

 continued in the hiboratory: NUzcJua cJosteriwin^ Nitzchia sp. (very 

 small diatom from California), Carteria sp. (green alga, family 

 Chlamydomonadinae), Cromulina sp, (greenish alga, order Chryso- 

 monadinae). and an extremely small, pink microorganism not yet 

 identified. The latter form was isolated from the samples collected 

 on oyster beds in Great South Bay, where oysters developed unusually 

 dark pigmentation. 



By using various combinations of inorganic salts and organic 

 substances, a method has been perfected whereby very dense cultures 

 of diatoms can be obtained. At present, the richest culture growing 

 in the laborator}^ contains 1,400,000 diatoms in each cubic centimeter 

 of water. Under proper light and temperature conditions, this dense 

 population can be maintained almost indefinitely by withdrawing' 

 every da)^ a portion of the culture and replacing it with an equal 

 amount of solution. It is intended to apply this method in producing 

 large quantities of diatom cultures and in using them for artificial 

 feeding of oysters. 



THE USE OF SLAG IN OYSTER CULTURE 



A series of experiments was performed with slag, a byproduct of 

 the steel industry, which has been recently brought to the attention 

 of oyster culturists as a material suitable for cultch. Experiments 

 carried out at Onset and Wareham River, Mass., showed that oyster 

 larvae readily attach to the surface of slag and grow well. Its 

 presence in water may increase the productivity of oyster beds, 

 because slag has been found not only to promote the growth of dia- 

 toms, but to maintain it for longer periods than in the control cul- 

 tures. The presence of slag on oyster beds is therefore of double 

 advantage, serving as a source of nutriment to the oyster food as 

 well as material for the attachment of spat. 



The growth promoting factors of slag may be extracted by repeated 

 boiling in sea water — diatoms growing rapidly in the filtrate. 

 Untreated slag lumps as they are received from the mills are 

 highly favorable to growth. Some of the growth-promoting factors 

 of slag seem to be removable by alcohol washing, as growth in cultures 

 containing alcohol-washed slag, while more prolonged than the 

 growth in the controls, is not so rapid as in cultures containing 

 untreated slag. 



OYSTER PLANTING IN NORTH CAROLINA 



In order to rehal)ilitate the depleted natural o.yster beds of this 

 State, transplantation of seed oj^sters has been carried out under 

 the direction of Dr. H. F. Prytherch. in cooperation with the North 

 Carolina Department of Conservation and the Civil Works Admin- 

 istration. These operations have been conducted in 5 coastal counties 

 where during December 1933 a total planting of over 272,000 bushels 

 of seed has been made at an average cost of aproximately 9 cents per 

 bushel. In order to maintain producticm of the areas' from Avhich 

 seed oysters have been obtained, large quantities of old oyster shells 

 have been scattered over the bottoms to provide a place of attach- 



