OF THE ACTINOPHRYryA. 559 



Their movements are excessively slow, and sometimes inappreciable ; and the 

 tentacles appear not concerned in them: conjugation is of very frequent 

 occurrence. 



The genera enumerated in this section are Act'inophrys, Podophrya, Tri- 

 chodiscus, and Dendrosoma. The distinction between the two fii'st-named 

 genera is denied by Stein, and probably with reason, for the stem of Podo- 

 fhrya is not sufficiently characteristic {vide Part I. p. 243). Trichodiscus is 

 little known to observers, and probably is only a variety of Actinophrys ; and 

 Dendrosoma has hitherto received little attention ; its branched pedicle, how- 

 ever, gives it a generic importance. 



Dujardin formed a very correct conception both of the organization and 

 affinities of the Actinophrjina, which were coupled with Amoebaea and Ehizo- 

 poda in his second order of Infusoria. He rejected the genera Podophrya 

 and Trichodiscus, which he merged in the genus Actinophrys. Siebold very 

 strangely overlooked the true structm^e and affinities of Actinophrys, which 

 he placed with Enchelia, in company with the very dissimilar Prorodon, 

 among his " Stomatoda." 



Perty has constituted Actinophryina a second section of Ciliata, and has 

 adopted the genera Actinophrys, Podophrya, and Acineta. Trichodiscus he 

 regards as only a compressed form of Actinophrys, and treats Dendrosoma 

 as an aggregated one, in which the individual beings are collected into 

 colonies. 



Genus ACTINOPHRYS (XXIII. 28-32).— Body more or less spherical, 

 usually compressed or discoid, sometimes iiTegular in outHne, owing to the 

 projection of superficial vacuoles. Tentacles tapering, terminated occasionally 

 by a rounded head (i.e. capitate), pretty uniformly distributed, their length 

 generally exceeding the diameter of the body ; retractile, and for a time lost 

 in the substance of the body, but reappearing at the same place and under 

 the same form. The tentacles serve for prehensile instruments, but not for 

 locomotion. Food is introduced within the body at any part, and not through 

 a mouth ; and its excrementitious portion is in a similar manner discharged 

 from any part of the exterior. Internally are one or two contractile vesicles, 

 placed immediately beneath the surface, a nucleus with a nucleolus, ali- 

 mentary vacuoles, granules, and probably smaU nuclear cells. Reproduction 

 takes place by fission, and in Dendrosoma by gemmation. Germinal deve- 

 lopment is presumed, and conjugation is a frequent phenomenon. 



The proboscis mentioned by Ehrenberg appears to be a sort of expansion 

 of the sarcode of the body, homologous mth a variable process, which enve- 

 lopes and then drags the prey into the general mass. 



Ehrenberg believed he had discovered a mouth, anus, and polygastric 

 structure, and that he had succeeded in demonstrating this last by feeding 

 with coloured food. He hkewdse adopted Eichhorn's statement — that the 

 tentacles acted as locomotive organs, by giving the animalcules the power to 

 crawl. 



The specific distinctions hitherto attempted are really of little worth ; even 

 the highest authorities are in doubt, and disagree among themselves, respect- 

 ing the specific names of the animalcules they so elaborately describe ; and 

 the revision of the several forms and varieties of Actinophrys is urgently re- 

 quired before any satisfactory separation into species can be made. We 

 append those forms which have been accounted specific by diiFerent authors. 



AcTiNOPimYS Sol (xxiii. 28, 31, 32). I spherical, or nearly so ; the tentacles or 

 Colour whitish, or rather grey; figure j rays divergefrom every part of the sm-faee. 



