142 



BULLETIN OF THE BUREAU OF FISHERIES. 



diatom caused the greening, Narragansett Bay was studied in a general way with 

 respect to its diatom growth. In samples taken in different parts of the bay and in 

 sheltered locations along some of its inlets no diatoms that in any way answered the 

 description of Navicula ostrearia were found. Further than that no classification of 

 American diatoms that could be obtained gave any description of a Navicula of the 

 characteristics that were typical of the organism found in the southern waters. 



Following are the results of the examination of water samples from Narragansett 

 Bay: 



The examination of the alimentary canal of 13 oysters with greengills which arrived 

 some three or four days after shipment from Virginia showed in every case the presence 

 of Navicula ostrearia f rustules in the digestive tract. In 8 oysters the stomach contents 

 were examined; in 3 the intestines were opened and their contents examined; while in 

 the 2 others excrement was obtained from the rectum and in every case the presence of 

 the sought-for frustules was determined. 



NAVICULA FUSIFORMIS var OSTREARIA. 



Lankester describes the Navicula fusiformis var. ostrearia, as a minute spindle-shaped 

 diatom which measured about ^j^ of an inch in length and tz^is of ^^ inch in breadth. 

 It has two long and relatively large yellow-brown endochromes stretched out parallel to 

 the surface of the organism, while at the tip ends, or scattered sometimes throughout the 

 length of the organism, was a pale blue-colored protoplasm. The Navicula has a cen- 

 trally located nucleus and several vacuoles located at intervals along its length. 



The organism found in Virginia compares almost exactly with this description. Its 

 measurement, obtained in this investigation, was about -.^ to -j^ of an inch in length, 

 while in breadth at its broadest point it was found to be between -^ ^^ a and ^ 5^0 g of 

 an inch. In only this one particular are the observations at variance with Lankester's, 

 but it is believed that either his drawings are not proportional to his measurements or 

 there has been some typographical mistake in stating that the width of the organism at 

 its greatest breadth is 7^517 of an inch. Indeed, that measurement would mean that the 

 organism was about 3 micra in diameter, which is absurdly small. The mistake is believed 

 to be one of typography and not of scientific inaccuracy, since Lankester's drawings show 

 the length and breadth relationship of his organisms to be exactly what was observed in 

 the diatoms of the Virginia epidemic. The two endochromes, yellowish-green in color, 

 were exactly analogous to those which Lankester deals with in his paper, while the blue 

 protoplasm was also found in analogous locations, usually in the tip ends, but sometimes 

 distributed throughout the entire length of the diatoms. Under changes in osmotic 

 pressure the blue pigment, as well as the yellow-green endochromes, was affected. The 

 blue pigment, which under ordinary conditions was held near the ends of the diatom, 

 was freed suddenly from its location. It was diffused sometimes throughout the body of 



