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BULLETIN OF 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, Sagittae, 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 (1880) 
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 scidpin ( Acanthocottus groenlandicus 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 
medusae, 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 NyctipJianes couchii. 
Paulsen (1909, p. 48) records Thysanoessa inermis from Icelandic waters stuffed 
with the diatoms Asterionella, Chsetoceras, 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 
Meganyctiplianes 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 
Meganyctiplianes 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 
