170 BULLETIN OF THE BUREAU OF FISHERIES 



square and cubic meter for that summer and for the season of 1915 are tabulated in 

 an earlier report (Bigelow, 1917, pp. 315 and 319). September stations for 1915 

 yielded an average of about 65,000 copepods per square meter in the northern half 

 of the gulf — no noticeable change, that is, from the midsummer state — but the fact 

 that the maximum (173,000) was considerably less and the minimum (14,700) con- 

 siderably greater is interesting as evidence that copepods tend to become progres- 

 sively more and more nearly equalized in number over the gulf as the season advances. 



In the earlier chapter I have pointed out that we have observed an autumnal 

 increase in the amount of plankton present in the western and northwestern parts 

 of the gulf (p. 87). In 1915 this was due to a multiplication of copepods from the 

 September average just given to an average of about 107,000 per square meter at 

 ten stations for the month of October (stations 10323 to 10329 and 10336 to 10339; 

 table, p. 297). As evidence that this multiplication was due to increased local repro- 

 duction we found upwards of 200,000 off Cape Cod (station 10336) and in Massa- 

 chusetts Bay (station 10338) on the 26th and 27th. 



Unfortunately no vertical hauls have been made in the gulf in November, 

 December, or January. It is therefore impossible to follow numerically the gradual 

 decimation of the local stock of copepods which takes place during the winter (p. 88), 

 leading to the sparse copepod population of early spring (p. 82). 



Outside the continental edge the numbers of copepods have invariably been small, 

 except for the one Calanus swarm of March just mentioned, the origin of which is 

 discussed under that species. 



The pelagic copepods are perhaps the most truly planktonic of all animals, for 

 although some of them dart actively through the water, and all swim more or less 

 vigorously, they are utterly at the mercy of the current so far as directive journeyings 

 from place to place are concerned. Most of the copepods of the Gulf of Maine are 

 eupelagic ocean forms, floating at various depths beneath the surface of the water by 

 means of their elongated first antennte. The two species of Acartia (clausi and 

 longiremis) , the two species of Calanus {finmardiicus and hyperboreus) , the two species 

 of Metridia (longa and lucens) , and Pseudocalanus elongatus, which together constitute 

 80 per cent of the copepod plankton of the gulf, all belong to this class. 



The scope of the present paper being ecologic and geographic, not systematic, the 

 copepods are arranged alphabetically here, the list of species, the distribution of which 

 is discussed, being as follows. Those starred are only accidental in the plankton. 

 For supplemental notes on a few other rare species detected by Dr. C. B. Wilson after 

 the body of the report was ready for the press see p. 305. 



Centropages hamatus. 

 Centropages typicus. 

 *Dactylopusia thisboides. 

 Dwightia gracilis. 

 *Ectinosoma neglectum. 

 Eucalanus attenuatus. 



Acartia clausi. 

 Acartia longiremis. 

 Acartia tonsa. 

 Aetidius armatus. 

 Anomalocera pattersoni. 

 Asterocheres boecki. 

 Calanus finmarchicus. 

 Calanus hyperboreus. 

 Candacia armata. 

 Centropages bradyi. 



Eucalanus elongatus. 

 Euchceta media. 

 Euclweta norvegica. 

 Euehirella rostrata. 



