BIGELOW: OCEANOGRAPHY OF MASSACHUSETTS BAY. 415 



in all directions. No doubt the strong tides and currents which flow 

 over the Bank keep them afloat. They were submitted to Prof. S. F. 

 Clarke for identification, and will be described more fully elsewhere. 

 Large nmiibers of haddock eggs, nearly ready to hatch, were like- 

 wise found in the haul. The microplankton was decidely more 

 abundant than the larger organisms, so much so, that, according to 

 Mr. Douthart's accounts, the nets were soon clogged, although of 

 large mesh. And he further noted that it was in streaks, not uni- 

 formly distributed. On microscopic examination, the mass proved 

 to consist of diatoms ; but qualitatively it was far more complex than 

 the diatom swarm near shore, while the chief role was played by 

 various species of Chaetoceras, especially C. densum, C. atlanticum, 

 and C. decipiens, instead of by Thalassiosira, although T. norden- 

 skioldi and T. gravida were both abundant. Other conspicuous 

 species are Ditylum brightwellii, Rhizosolenia ohtusa, R. styliformis, 

 R. semispina, Thalassiothrix nitzschioides, Coscinodiscus, Coscinosira 

 Asterionella japonica, with large numbers of Pleurosigma. 



A little more than a Aveek later, Mr. Douthart made a second series 

 of tows on the western side of the Bank (p. 419), which showed that 

 the macroplankton was apparently less abundant; and though it was 

 of the same general type as before, Temora was about as abundant as 

 Calanus. But the fact that the hauls were restricted to the surface 

 makes it doubtful whether apparent variations in the relative numbers 

 of different organisms have any real meaning. Other characteristic 

 members of the plankton were Sagitta elegans, Oikopleura, the cam- 

 panularian hydroids noted above, Actinian larvae, Hybocodon, 

 Pleuwbrachia pileus, and many haddock eggs. The microplankton 

 was quantitatively as rich as on the last visit ; but it had undergone a 

 decided change qualitatively, its most important component, numeri- 

 cally, now being Rhizosolenia styliformis. In the last haul, this form 

 was represented by occasional examples only; now it formed the 

 greater part of the mass; and many of the specimens were so large 

 (1.1 mm.) as to be easily visible with the naked eye. 



