Gonyaulax and the Discolored Water 

 in the Bay of Agu. 



T. Nishikawa. 



During the latter part of September, the streaks and patches of 

 brownish-yellow water emitting an unpleasant odor were observed by 

 fishermen in the Bay of Agu, situated in the southern part of the 

 Province of Shima, on the Pacific side of the Hondo. As this '" red-tide" 

 is said to have been in former times highly destructive to the beds of the 

 pearl-oysters which form one of the principal productions of the Bay, a 

 great alarm was felt for the safety of the Molluscs. Fortunately, 

 however, on the 28th of the month, a heavy storm arose and cleared 

 the waters of the Bay, so that very little damage was actually done. 



By the order of His Excellency, the Minister of Agriculture and 

 Commerce, I visited the Bay to determine, if possible, the cause of the 

 unusual coloration of the sea-water. 



According to the observations of Mr. Mikimoto, a pearl-oyster 

 culturist of Tadoko Island in the Bay, the surface waters on the southern 

 coast of the Island and along the shore of Hasako, were on the 23 rd of 

 the month densely discolored. But, when I arrived at the Island on the 

 25th, this discoloration of the water had almost disappeared. I was told 

 by a fisherman that patches of discolored water were to be seen on 

 he northern shore of Masaki Island, but unfortunately it was already- 

 twilight when I arrived there by a boat on the evening of the 25th 

 Consequently it was impossible to distinguish clearly any coloration 

 but by an unpleasant odor I was able to recognize the presence 

 of the discolored water. The odor of the discolored water was 

 similar to that which is emitted by the Algae when collected in a great 

 quantity. On next day, I was fortunate enough to observe well such a 



