BIGELOW: THE "GRAMPUS" IN THE GULF STREAM. 199 



lower part of the net was completely filled with them. The quantities 

 in these hauls were, however, much less than would have been taken in 

 surface hauls of like duration, indeed no more than would be gathered 

 on the surface by the five-foot net in two or three minutes. This fact in- 

 dicates that the Salpae were chiefly limited to a comparatively shallow 

 surface zone, probably not more than 20 or 30 fathoms, and that it was 

 on its passage downward and upward through this zone, not while being 

 towed horizontally at from 150 to 300 fathoms, that the intermediate 

 net captured the load of Salpae which it invariably yielded. 



The diminution in the number of Salpae noted on leaving the warm 

 water of the Gulf Stream on our homeward trip was sudden. Thus 

 while at Station 13, lat. 39° 57', long. 70° 13', eight quarts were taken in 

 an intermediate haul ; in lat. 40° 7', long. 69° 59' (Station 14), where 

 the surface temperature had dropped from 72° to about 70° the diminu- 

 tion was already marked, and at Station 15, only twenty-seven miles dis- 

 tant, but with a surface temperature of 64°, only two or three individuals 

 were seen and none taken during the half hour occupied in making a tow 

 with the five-foot net at 15 fathoms. After this point, on the run north- 

 ward around Cape Cod, only a few scattered individuals were observed. 

 I may call attention here to the fact that Salpae were unusually abun- 

 dant at Woods Hole throughout the summer of 1908. 



The abundance of Salpae caused the quantitative richness of the sur- 

 face Plankton of the Gulf Stream to be extremely high. But, as is 

 usually the case when any one large organism is swarming throughout a 

 considerable period, the yields of the surface hauls were qualitatively 

 correspondingly poor. This poverty was progressive throughout the 

 cruise, a fact suggesting that we reached the Stream early in the swarm- 

 period of the Salpae, and that as time progressed these rapacious organ- 

 isms devoured most of the smaller forms which usually compose the bulk 

 of the surface Plankton. Indeed, considering the volume of water 

 strained by them, but few of the smaller copepods, pteropods, or pro- 

 tozoans could be expected to escape. An unusual transparency of the 

 surface water was connected with the poverty of the finer Plankton. 

 For example, at Station 9, where it happened that fewer Salpae than 

 usual surrounded the ship, the five-foot net was distinctly visible at 

 a depth of 20 fathoms. 



The Plankton, aside from the Salpae, presented no unusual features, 

 except in the absence of certain forms which are usually common. Very 

 few pelagic fishes were taken, among them being Cyclothone, and several 

 mictophids. Among crustaceans, schizopods, particularly Euphausiidae 



