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BULLETIN OF THE BUREAU OF FISHERIES 
smaller copepods form a considerable item in the diet of Temora. Calanus, however, 
she found chiefly vegetarian, and Pseudocalanus perhaps exclusively so. Marshall’s 
(1924) more recent study of the gut contents of large numbers of Calanus taken 
throughout the year in the English Channel corroborates this, diatoms proving the 
chief article of diet in spring and autumn with peridinians (curiously enough, however, 
no Ceratium) in summer. Silicoflagellates were also eaten in small quantities, 
while a few of the Calanus had eaten other copepods, molluscan larvae, and tintinnids. 
All the Tomopteris I have examined have been empty, which has been the 
experience of most students, but it is probable that they are vegetable feeders chiefly, 
Lebour (1922 and 1923) having found diatoms their principal diet, with some green 
flagellates. Tomopteris, however, sometimes turns carnivorous, for she watched 
one swallow a Sagitta whole and saw another that contained a larval herring. All 
the shell-bearing pteropods ( Limacina retroversa, for example) are also vegetarian, 
dieting chiefly on diatoms. The Salpse likewise feed on diatoms, peridinians, and other 
small organisms, animal as well as plant, their gut contents and foecal masses having 
long been a treasure house to the student of the microscopic plankton. For example, 
the “guts” of large S. tilesii collected south of Nantucket Lightship in July, 1913 
(station 10061), contained a varied assortment of diatoms, Peridinium, and Ceratium, 
besides an occasional newly-hatched Euthemisto; but the most successful captors 
of the unicellular pelagic plants are the appendicularians, which, thanks to their 
very fine-meshed straining apparatus, are able to utilize gymnodinids, rhizopods, 
naked flagellates, coccolithophids , 52 etc., forms so tiny that for the most part they 
pass through the finest tow nets. Appendicularians likewise devour the larger 
protozoans and unicellular plants. For example, a large OiTcopleura vanhoffeni from 
the neighborhood of Lurcher Shoal (May 10, 1915, station 10272) was packed with 
the horns and other fragments of Ceratium, besides small Peridinium of several 
species, tintinnids, and silicoflagellates (Distephanus). 
None of the pelagic tunicates are plentiful enough in the Gulf of Maine to make 
serious inroads on the phytoplankton. In the Gulf Stream to the south Salpse 
sometimes occur in hordes, and on such occasions strain the water bare (Bigelow, 
1909). 
Among the unicellular planktonic animals the infusorians are proverbially rapa- 
cious. The tintinnid genus Cyttarocylis has been found to contain a great variety 
of microsocopic organisms — e. g., Peridinium, Dinophysis, Goniaulax, and diatoms 
(Lebour, 1922) — and even the Infusoria, which are provided with chromatophores, 
are known to take solid food (Steuer, 1910, p. 627). Radiolarians engulf diatoms, 
tintinnids, and other Infusoria; hence, when Acanthometron swarms in the gulf 
(p. 460) it must locally take heavy toll of other microscopic animals and of planktonic 
plants. Foraminifera are also rapacious animals, but have never been found plentiful 
enough in the plankton of the Gulf of Maine to be of any great importance in the 
economy of its planktonic communities. 
On the border line between plant and animal, so far as their mode of nourishment 
is concerned, stand the peridinians, for while the shelled forms are typical producers 
42 For an account of the food of appendicularians see Lohmann (1903, p. 23, pi. 4) and Johnstone (1908, p. 139). 
