PLANKTON OP THE GULF OP MAINE 109 



Cod on December 29, 1920 (station 10491), had a dozen or more Metridia and as many 

 Pseudocalanus. live or six large Calanus, the siphon and part of the stem of a Ste- 

 phanomia, besides a considerable mass of diatoms (Rhizosolenia) and some unrecog- 

 nizable animal debris clasped between its thoracic legs. Several others taken at 

 random from a large catch of these shrimps, made in the northeastern corner of the 

 gulf on June 10, 1915 (station 10283), carried packs consisting chiefly of Calanus, 

 occasionally a Eucha?ta, and Pseudocalanus, matted together with unrecognizable 

 vegetable debris. One had a starfish larva and two eggs, probably of its own species, 

 with the young nauplius almost ready to hatch out. Lest the reader think this 

 omnivorous diet is at all seasonal, I may add that most of the Meganyctiphanes 

 taken in the eastern basin on August 7 of that year carried loads of Calanus, Metridia, 

 and Temora, with the cladoceran genus Evadne in great numbers, besides algal 

 filaments and debris, the origin of which I could not determine. At Eastport, 

 too, I have seen Meganyctiphanes clasping bits of herring refuse from the sardine 

 factories. 



Up to very recently the method by which euphausiids gather their food had not 

 been actually observed in life, but since the preceding lines were written, Lebour 

 (1924a, p. 405) has described the food as "brought to the thoracic limbs by a current 

 from behind, set up by the movement of the abdominal limbs, the thoracic limbs 

 forming a sort of basket-hke receptacle for the accumulated food." Thus with the 

 bristly armature of their legs they sweep the water for their prey just as barnacles 

 do, gathering whatever copepods, Cladocera, diatoms, peridinians, or indeed small 

 animals or plants of any sort, come within their reach as they dart to and fro in the 

 water. 



The nourishment of the marine copepods remained a riddle until Dakin (1908) 

 found that the alimentary canals of hundreds of Calanus, Pseudocalanus, Centro- 

 pages, and other genera of copepods from the North Sea contained chiefly diatoms. 

 He counted up to 200 diatom shells in the stomach of a single copepod, with peridin- 

 ians and a green substance (previously noted by other students), apparently the remains 

 of shell-less unicellular plants. Esterly (1916) has similarly described the contents 

 of the guts of several hundred copepods (mostly Calanus) from San Diego, Calif., 

 as consisting chiefly of Coscinodiscus and other diatoms, silicoflagellates, Dinophysis, 

 Peridinium and other peridinians, and of coccolithophorids. Lebour (1922) also 

 found diatoms of various species, Phasocystis, coccoliths, and peridinians in Calanus; 

 diatoms and green remains in Pseudocalanus; diatoms and flagellates in Temora; 

 and Pha?ocystis in Anomalocera. 



Murphy (1923, p. 450) writes that the copepod Oiihona nana ate kelp and 

 diatoms in the aquarium, and we have recognized remnants of Thalassiosira in sundry 

 specimens of Calanus, and Thalassiosira, Chsetoceros, and Biddulphia in Metridia 

 from Massachusetts Bay at the time of the vernal diatom flowering. Diatom frag- 

 ments have also been detected repeatedly in the excreta of copepods, which are 

 familiar objects in the catches of tow nets, but Esterly's (1916) discovery of an oc- 

 casional nauplius and copepod fragment in copepod stomachs proved that they 

 are not exclusively vegetarian. Lebour (1922) has more recently found that 

 the large blue copepod Anomalocera may feed largely on micro- Crustacea, while 



