PLANKTON OF THE GULF OF MAINE 



337 



The bathymetric range of T. catharina in the gulf is considerable. We have 

 taken it on the surface at four stations in August, two in March, and three in April.' 9 

 In connection with the relationship of Tomopteris to temperature, discussed below, 

 it is interesting that the surface captures in summer have all been in the northeast 

 part of the gulf — that is, on German Bank, near Lurcher Shoal, and off the eastern 

 coast of Maine — whereas the localities where we have taken it on the surface in early 

 spring include Massachusetts Bay and the general neighborhood of the Isles of 

 Shoals in the western side as well as German Bank in the eastern. 



At the other extreme T. catharina certainly occurs as deep as 180 meters (closing- 

 net haul at station 20079, March 22, 1920), and probably down to 200 meters, if 

 not still deeper, though the majority of captures have been in open-net hauls from 

 40 to 150 meters depth. When the actual depths of the individual hauls yielding 

 Tomopteris are classified by months, its bathymetric distribution appears decidedly 

 uniform from season to season, as illustrated by the following partial list of the cap- 

 tures for midsummer as compared with early spring: 



Partial list of the captures of Tomopteris for midsummer, as compared with early spring 



MIDSUMMER 



EARLY SPRING 



'Surface net. 



'Closing net. 



Although T. catharina has not yet been detected in the bottom water of the deep- 

 est trough of the gulf, it is to be expected there, for off Ireland it occurs indifferently 

 from the surface down to more than 1,000 meters depth (Southern, 1911). Our sur- 

 face catches, like Huntsman's (1921, p. 87) were with one exception between 6 p. m. 



" The surface records are as follows: Stations 10030 and 10032, Aug. 14 and 16, 1912; stations 10245 and 10247, Aug. 12 and 13, 

 1914; stations 20O60 and 20085, Mar. 4 and 23, 1920; stations 20092, 20093, and 20119 .Apr. 9 and 20 .1920. 



