130 bulletin: museum of comparative zoology. 



The richest zooplankton (p. 99, 100) both in volume and in the 

 number of copepods, was found in the northern part of Massachusetts 

 Bay, off Cape Ann, in Ipswich Bay, over the western arm of the 100- 

 f a thorn basin, off Cape Porpoise, and on Piatt's Bank; the poorest, in 

 the Grand Manan Channel, and along the northeast coast of Maine, 

 where the water was almost barren (p. 104). In the cold fresh water 

 along the southern coast of Maine, and in general over the northeast- 

 ern part of the Gulf along the west coast of Nova Scotia the richness 

 of the plankton was intermediate, column 2 in preceding table. Along 

 shore from Casco Bay to Penobscot Bay it was poor on our first visit 

 early in August, but with a rich diatom plankton; and on our return, 

 this type of plankton was found from Petit Manan to Penobscot Bay; 

 but off the Penobscot and the Kennebec Rivers there were more 

 copepods, enough to bring the hauls into column 2. 



MlCROPLANKTON. 



The microplankton will be the subject of a special report, conse- 

 quently no attempt is made here to identify all the species. But its 

 character varies so much at the different stations, and proves so char- 

 acteristic of different regions, that the following notes are pertinent. 



An examination of the hauls with the no. 20 net, made at Stations 

 1, 6, 7, 8, 9, 12, 12a, 13, 16, 17, 19, 21, 21a, 22, 23, 24, 25, 26, 26a, 

 27, 28, 29, 30, 31, 32, 33, 34, 35, 36, 37, 38, 39, 40, 41, 42, 43, 44, 

 as well as at various localities in Casco Bay, shows that the micro- 

 plankton was of two principal types, one consisting chiefly of the 

 peridinian, Ceratium tripos, the other of various diatoms, mainly 

 species of Chaetoceras and Rhizosolenia. The diatom plankton 

 usually contains a few Ceratium; and at several localities the two 

 types are mixed together. Quantitatively, too, as well as qualita- 

 tively, there is much variation between the hauls made in different 

 parts of the Gulf (Plate 8) though our brief period of work throws no 

 light on seasonal fluctuations. 



At our first few stations, in the northern half of Massachusetts Bay 

 and in the neighborhood of Cape Ann, the microplankton proved to be 

 very scanty in amount, consisting of a few Ceratium, an occasional 

 Peridinium, hardly any diatoms in spite of proximity to land; but a 

 considerable number of eggs and larvae of various Metazoa, chiefly 

 copepods. And when we returned to Massachusetts Bay in the latter 

 half of August, no apparent change had taken place, the hauls at 



