BIGELOW: COAST WATER EXPLORATION OF 1913. 267 



THE PLANKTON. 

 General account of the macroplankton. 



The plankton work of the cruise had two main objects : — ■ first, 

 a quaUtative survey of the various species, which must precede any 

 quantitative study to make the latter valuable; and, secondly a 

 faunistic examination of the plankton as a whole, at each station, 

 to illustrate the geographic occurrence of associations of species. 



When the work in Massachusetts Bay in May, 1913, was finished the 

 vernal diatom swarm had largely disappeared, and copepods, which 

 had been very scarce during the preceding month, had reappeared in 

 the shape of swarms of nauplii and older larvae ; while by June, hauls 

 off Gloucester yielded an almost pui-e Calanus plankton. Much this 

 same condition obtained early in July, surface hauls off Gloucester, 

 on July 7th, yielding a rich harvest of Calanus finmarchicus, with great 

 numbers of the large blue copepod Anomalocera pattersoni, together with 

 young schizopods, and a few other boreal organisms; while the im- 

 portance of this region as a spawning ground for food fish was attested 

 by the presence of numerous gadoid fry in the nets. 



The hauls off Cape Cod (Station 10057) revealed the same type of 

 macroplankton that occupied the greater part of the Gulf during the 

 summer of 1912, namely, swarms of Calanus finmarchicus, a few Eu- 

 chaeta norvegica, many small schizopods (Thysanoessa) , Euthemisto 

 and Hyperoche among amphipods, the pteropod Limacina balea (p. 

 303) ; Sagitta clcgans (p. 299) ; the Medusae Staurophora mertensii and 

 Mclicertum campanula; the siphonophore Stephanomia cara (p. 315); 

 and the ctenophores Beroe cucumis and Pleurobrachia pileus. Al- 

 though open nets alone were used, their contents clearly showed that 

 the plankton was bathymetrically stratified. Thus it was the surface 

 hauls alone that yielded any considerable number of copepod nauplii 

 and eggs; and while the haul at 15-0 fathoms caught swarms of 

 Calanus, and many schizopods, and hyperiids, but only a few Sagittae, 

 the haul from thirty fathoms contained almost no schizopods, hyperi- 

 ids, or pteropods, but on the other hand brought back great numbers 

 of Sagittae; and Euchaeta was taken in the deep haul only; i. e., Ca- 

 lanus, schizopods, hyperiids, and pteropods were mostly above fifteen 

 fathoms, Euchaeta, and Sagittae below that depth, Beroe, Pleuro- 

 brachia, and Stephanomia more evenly distributed horizontally. 



