KOFOID AND SWEZY: UNARMORED DINOFLAGELLATA 49 



partly crushed together within its body (fig. PP, 2). The contents liad evi- 

 dently been digested and the remains were being forced to the posterior region 

 of the body preparatory to ejection when the Pouchetia escaped from the 

 cyst. The Pcridinium here captiired is a large species, the length of the body 

 equaling that of the organism which has devoured it, as may be seen from the 

 length of the half-shell which is visible in the figure. 



Pouchetia, like the genus Erijthropsis, has no species which possesses chro- 

 matophores. A few of the species of the former and all the latter failed to 

 show the presence of food Iwdies in the cytoplasm. With the small number 

 of species and individuals observed, however, this is not conclusive evidence 

 as to its manner of food-taking. It is probable that nutrition is either sapro- 

 phytic or more probably holozoic in both genera. 



The same conditions that have been observed in the forms discussed here- 

 with obtain in the other members of the Gymnodinioidae. One of the most 

 rapacious feeders is NoctUuca. This seems to devour indiscriminately any- 

 thing of an organic or even an inorganic nature that comes in its way; the 

 authors have observed on two occasions the presence of grains of sand within 

 it nearly as large as the body. Both these individuals were lying on tlie sub- 

 strate apparently imable to rise above it. 



In this brief review of these forms it has been shown that there is an upward 

 progression from a chromatophore-bearing, holophytic t^'pe of nutrition in 

 Aniphidiniion, which has probably been carried over from the holophytic 

 cry])tomouads, to a saprophytic and holozoic type in the more advanced mem- 

 bers of the group. In some species both tj^pes are intermingled, others are 

 more clearly marked off as having a single t\TDe of nutrition. The demarcation 

 between the saprophytic and holozoic types is still more difficult to define siiice 

 those belonging to the latter group resemlile the saprophytic forms when food 

 bodies are not present. It is possible that all three types ma}' be found in a 

 single individual. 



The presence of pusules in these organisms is signifieant in this connection. 

 The process of taking the surrounding medium into the body through the 

 pusules, its passage through the cytojjlasm and escape at the surface is prob- 

 ably correlated with a saprop]i3'tic method of food-taking. The relatively huge 

 size of the pusule apparatus in the thecate forms may be due to the lack of free 

 access of the surrounding fluid to the cytoplasmic body. Many species of the 

 dinoflagellates are never captured in surface hauls, but are found within the 

 deeper layers of water, which are also the layers most rich in decaying plankton 

 and hence most suited to saprophytic organisms. 



A fourth mode of food-getting is also present in this group, that is, the 

 parasitic type found in the Blastodiniidae. Some of these, as Blastodinium 

 pruvoti (Chatton, 1906), may be only a conmiensal in the intostiue of the host, 

 Paracalanus parvus, or they may be truly parasitic, as in CItijtrio(linii(»i roseum, 

 which feeds upon the contents of the egg of a copepod (Doflein, 1911). Still 



