BIGELOW: EXPLORATIONS IN THE GULF OF MAINE. 133 



and Peridinium. As we approached the mouth of the Grand Manan 

 Channel (Station 33), Ceratium was no longer found and the micro- 

 plankton became very scanty, just as the macroplankton did (p. 104), 

 consisting of various diatoms, chiefly Chaetoceras and Asterionella : 

 and it grew poorer and poorer as we sailed eastward. In the Channel 

 the microplankton was very scanty indeed, purely diatom, several 

 species of Chaetoceras, and Asterionella being the most important 

 forms, with a few Thalassiothrix, etc. 



The poverty of the microplankton in the Channel was paralleled, to 

 an even more extreme degree, by the macroplankton, and is one of the 

 most interesting observations made on the trip, as the fact that herring 

 occasionally swarm here shows that at times the plankton must be 

 much more abundant than we found it. 



On the voyage homeward Ceratium was once more met in con- 

 siderable numbers at Station 36, where the haul revealed a mixed 

 plankton of the t} r pe general over the Eastern basin. (Plate 8). 



On August 21, when passing Great Duck Island, one of the small 

 islands off Mt. Desert, the appearance of the water was noticeably 

 "soupy" and immediately the vessel was hove to, and a surface 

 haul made with the no. 20 net. When brought on board, the net was 

 filled with a brown slimy mass which, on examination, proved to 

 consist almost wholly of countless numbers of chains of Asterionella 

 japonica, with a few other diatoms, particularly Chaetoceras. This 

 phenomenon was so striking that we took frequent samples as we sailed 

 westward, finding that the Asterionella swarm continued for some 

 miles, though nowhere else was the mass of diatoms so dense as it was 

 off Duck Island. At Station 38 a surface haul revealed much the same 

 type of microplankton, but less dense, with more Chaetoceras, and a 

 few Peridinium, but no Ceratium. During the following night, while 

 running from Station 38 to Station 39, a surface tow, abreast of the 

 mouth of" Penobscot Bay, was made to ascertain the extent of the 

 Asterionella swarm; this tow revealed a diatom plankton, chiefly 

 Asterionella, very much like Station 38, but rather less in amount. 

 But at Station 39, we had evidently passed out of this belt, for though 

 our hauls yielded many diatoms, there were also many Ceratium 

 tripos; i. e. we were once more in the region of mixed microplankton ; 

 though the water was yet visibly cloudy. This phenomenon con- 

 tinued as we crossed the mouth of Penobscot Bay, until suddenly, 

 when some six miles off Seguin Island, there was a visible change and 

 the surface water grew perfectly clear. The vessel was at once hove 

 to, and Station 40 occupied, making a series of tows. The no. 



