22 THE HELIOZOA 



through the whole substance of the body (Pompholyxophrys, Rliaphi- 

 diophrys), and in a few forms (Elaeorhanis) a large coloured oil 

 globule is found in the endoplasm. In Actinosphaerium, where 

 digestion and assimilation occur in the endoplasm, that region of the 

 body is crowded with brownish refringent granules, leaving the ecto- 

 plasm relatively free. A few of the larger coloured droplets have 

 been described as fatty ; but the chemical nature of most of these 

 coloured bodies is quite unknown. 



Chlorophyll associated with differentiated chloroplasts is found 

 either in the endoplasm (some varieties of Actinosphaerium Eichhornii) 

 or in the ectoplasm (Rhaphidiophrys, Heterophrys, etc.). The nature and 

 origin of these bodies have been much debated ; some writers have 

 regarded them as the remains of green animals or plants ingested 

 as food ; Archer and Greeff maintained that they were in many 

 cases, at least, formed by the Heliozoa in which they were observed. 

 There can be little doubt, however, that they are in some cases at 

 least of the same nature as the Xanthellae that occur in Radiolaria 

 (see p. 97) and in Trichosphaerium among the Lobosa, and that 

 they are therefore independent organisms living in association with 

 the Heliozoa, and are not, as has been suggested, of endogenous origin. 

 Although we have at present very little information concerning the 

 history of these organisms in the Heliozoa, the observations of 

 Penard on green varieties of Actinosphaerium lend strong support 

 to this suggestion. This author found that the green cells are oval 

 in shape, 7-10 //, in length, and surrounded by a clear gelatinous 

 membrane. They possess a bell-shaped chromatophore, a spherical 

 pyrenoid, and in some cases a vacuole at one end. On crushing 

 the Actinosphaerium, these cells escape, and subsequently protrude 

 first one and then a second very delicate flagellum. He believes 

 the organism to be identical with the Palmellacean Alga Sphaero- 

 cystis Schroteri (Chodat). In other cases he has seen a large number 

 of flagellate organisms belonging to the genus Chlamydomonas 

 attached to the surface of an Actinosphaerium, and has shown that 

 they are actively attracted to the host. It is true that at present 

 it has not been proved that the Chlamydonionads actually enter the 

 ectoplasm of the Actinosphaerium and become the xanthellae ; but in 

 view of the proof recently published by Keeble and Gamble (10), 

 that the infecting organism of the Turbellarian Convoluta belongs to 

 the Chlamydomonadina, Penard's observation is very suggestive. 

 Awerinzew (1) has recently described the xanthella of Actino- 

 sphaerium as Zoochlorella actinosphaerii. 



In addition to the xanthellae, other organisms are occasionally 

 found in the ectoplasm of the Heliozoa. Thus, a eiliate infusorian 

 allied to the genus Blepharisma has been found in as many as 

 30 per cent of the individuals of Rhaphidiophrys viridis found at 

 Bernex, and a rotifer attributed to the genus Monolabis by Archer 



