108 BULLETIN OP THE BUREAU OF FISHERIES 



several coelenterates, and especially the ctenophore genus Pleurobrachia, a pirate 

 to which no living creature small enough for it to capture and swallow comes amiss. 

 Small Crustacea of all kinds, other coelenterates, Sagittre, fish eggs, and even fish 

 of considerable size all are devoured, and so clean does it sweep the water with its 

 trailing tentacles that wherever these ctenophores abound practically all of the 

 smaller animals are soon exterminated. 



The larger ctenophore Beroe is even more voracious, though, fortunately for 

 the productivity of our seas, it is less numerous than Pleurobrachia. As Chun (1S80) 

 long ago observed and graphically described, Beroe feeds on its own relatives, even 

 on other ctenophores many times as large as itself, as well as on whatever else it can 

 capture. Lebour (1922 and 1923) found it dieting chiefly on Pleurobrachia, also 

 to some extent on other ctenophores and diatoms, while we ourselves have often found 

 Calanus and other copepods in its gastric cavity. 



Mertensia is no less voracious, for I have seen one individual of this genus 

 which "had entirely engulfed a young sculpin (Acanthocottus grcenlandicus Fabricius) 

 no less than 21 millimeters long, the victim being doubled up so as to fit into the 

 digestive cavity of its captor" (Bigelow, 1909a, p. 317). The various species of 

 medusaj, large and small, all belong to the piratical category, and the total destruc- 

 tion they wreak on euphausiids, copepods, appendicularians, the various larval forms, 

 etc., is beyond any estimation. Even animals as active and themselves as voracious 

 as Sagittae may fall victims to medusae (Obelia) far smaller, as Steuer (1910, p. 631) 

 describes. The siphonophores, too, of which our waters support one species in 

 abundance (p. 377), destroy countless copepods, etc. 



The common boreal euphausiids, important in the faunal community of the Gulf 

 of Maine, may typify the planktonic animals that feed chiefly on pelagic vegetables, 

 but which also consume animal food in less amount. Thus Lebour (1922) found 

 bits of green weed, diatoms, and fragments of mollusks in Nyctiphanes couchii. 

 Paulsen (1909, p. 48) records Thysanoessa inermis from Icelandic waters stuffed 

 with the diatoms Asterionella, Chaetoceras, and Coscinodiscus, and describes Megany- 

 ctiphanes as full of these same diatoms, with tintinnids (Cyttarocylis), peridinians 

 (Dinophysis, Ceratium, and Peridinium), and Globigerina in addition; but his dis- 

 covery of crustacean debris (Calanus antennae recognizable among it) in the stomachs 

 of both these species of pelagic shrimps proved that they had also eaten smaller 

 Crustacea — some of the specimens examined had, indeed, partaken of a purely 

 animal diet. Holt and Tattersall (1905, p. 103) likewise found some examples of 

 Meganyctiphanes with the leg basket more or less stuffed with prey, including 

 copepods, schizopods, and decapod larvae, Limacina and other animal debris, and 

 one with the tail of a young fish actually in its mouth. Lebour (1924a) reports 

 Meganyctiphanes feeding on Sagittae, Crustacea, and dead specimens of its own 

 kind in the aquarium. We can substantiate these observations in part, having 

 recognized algal filaments and diatom debris among the mass of finely comminuted 

 particles (themselves, to judge from their brownish green color, probably vegetable 

 in nature) with which the alimentary tracts of numerous specimens of Meganycti- 

 phanes from various parts of the gulf are packed, and we have often found specimens 

 of this shrimp carrying loads of small crustaceans. For example, one taken off Cape 



