PLANKTON OF THE GULF OF MAINE 



411 



expected to dominate the plankton in different regions, by our experience, arc laid 

 down on the chart (fig. 110). Our records show that it outnumbers or replaces 

 C. longipes first in the offshore parts of the gulf, and that it may be expected to pre- 

 dominate over the latter in the western and central deeps and in the eastern branch 

 of the basin north to latitude 43° or 43° 30' N. by mid-August. 



The following counts of samples from corresponding pairs of stations illustrate 

 how completely the relative importance of the two species is reversed between June 

 or the first half of July and the first days of August, and how nearly to the vanishing 

 point C. longipes sinks in these particular parts of the gulf as C. tripos multiplies. 



A corresponding preponderance of tripos (32 to 2 longipes) likewise characterized 

 a haul made by Capt. John McFarland off Chatham (Cape Cod) on August 26, 

 1913. 39 



The multiplication of or intrusion by C. tripos is apparently a slower process, 

 and C. longipes persists correspondingly longer as an important factor in the plankton 

 over the northeastern part of the basin. Thus in mid-August of 1914, when tripos 

 already greatly predominated right across the gulf along a line from Cape Ann to 

 Cape Sable, C. longipes still outnumbered it a few miles to the northward, as follows: 



Locality 



Number in samples 



C. 



longipes 



Off Lurcher Shoal Aug. 12, 1914, station 10245 



Extreme northeast corner of basin, Aug. 12, 1914, station 10246. 



Off Mount Desert Rock, Aug. 13, 1914, station 10248 



Off Penobscot Bay, Aug. 14, 1914, station 10250 



Off Cape Elizabeth, Aug. 14, 1914, station 10251 



105, 

 62 

 29 

 32 



115 



C 



tripos 



In 1913 longipes still continued about as numerous as tripos in the deep hauls 

 in the eastern side of the gulf (latitude about 43° 25' N., stations 10092 and 10093) 

 on August 11 and 12, by which date tripos was already predominant in the western 

 basin (stations 10088 and 10089). 



11 In the report on the cruise of 1912 the two species were listed together as tripos (Bigelow, 1914). 



