1921 J NATURAL SCIENCES OF PHILADELPHIA. Ill 



Such are the observations which I could make on Pteridomonas, 

 a very small and delicate organism, but one whose structure proves 

 very particularly interesting; and in my opinion the principal in- 

 terest attaches to the special threads or "flagellopodia," whose 

 functions are double, now pseudopodia, now flagella. Scherffelie, 

 1911, whilst treating of Chrysopyxis hipes and its pseudopodia, ob- 

 serves that the existence of food-capturing flagella has never been 

 proved in any of the Protozoa; but in Pteridomonas we find some- 

 thing quite exceptional: the food is caught by pseudopodia, the 

 undulating movements are due to flagella, but these very flagella 

 were pseudopodia some minutes before, and next moment will be 

 so again. 



Dimorpha tetramastix sp. n. Plate V, flgs. 4-6. 



''Cells with distinct periplast, free-swimming. Pseudopodia nu- 

 merous, with axial threads that radiate from a central granule 

 situated inside the body. Two flagella, originating in the neighbor- 

 hood of the central granule. Nuculus with distinct caryosome. 

 One to several contractile vesicles. . . ." 



Such is the diagnosis given by Lemmermann (in Pascher's ' 'SiJss- 

 wasser-Flora," p. 51) of the genus Dimorpha, which Gruber (14) 

 created in 1881 for a small Protozoan whose characters are at the 

 same time those of a Heliozoon and a Flagellate. 



Dimorpha mutans is the only species that has been described; 

 however, one other has been at least indicated. Blochmann (3), in 

 1894, after treating of Dimorpha mutans, concludes in the following 

 terms: "I myself found, in the summer of 1885 in a pond of the 

 Schwetzinger Garden, another form, of which I unhappily took 

 only a few incomplete sketches. It differed from D. mutans in 

 the possession of four flagella, and also in the fact that it always 

 swam about with fulty expanded pseudopodia." 



In the month of Juh^ last, and later in August and September, I 

 found in the same pond of the Ariana Park a species of Dimorpha 

 provided with four flagella. Is it the same as that mentioned by 

 Blochmann? Possibly so, but, as we shall see later, it is not cer- 

 tain. Is it even a Dimorphaf According to the first diagnosis of 

 the genus, which mentions two flagella, it is not; but, like Bloch- 

 mann, I should rather insist on the fact of the resemblance with 

 an Heliozoon than on the possession of one, two or more flagella. 



Dimorpha is indeed now a HeUozoon, and now a Flagellate. Let 

 us first consider our Dim. tetramastix in the Heliozoon, that is, in 

 the resting state (Plate V, fig. 4) : 



