OF THE ACTHSrOPHRYINA. 



561 



like. Its outline is double, with a green 

 or red line. Length 1-GOO" to 1-500"- 

 Bern. Among Confervae. 



A. Stella (Perty) = Tn'ckodiscus Sol.— 

 It is to be regretted that Perty, whilst 



recognizing this organism to be an 

 Actinophrys, should not have adopted 

 Dujardin's very appropriate name for it, 

 rather than encumber the student -udth 

 another. 



Genus TRICHODISCUS. — Body depressed, with a single marginal row of 

 setaceous tentacles ; vibratile cilia and teeth absent ; no pedicle ; mouth 

 truncated (Ehr.). 



These Infusoria, by their flat disciform shape, resemble Arcelhe, but, un- 

 like the latter, are soft and illoricated, with stiff, bristle-like rays. A central 

 opening, and a large lateral gland (nucleus), have been recorded by Ehren- 

 berg, who likewise states that he has seen, though indistinctly, numerous 

 digestive cells, but neither the reception of coloured food, nor an anal orifice. 



This account is very unsatisfactory as a. means of determining a genus. 

 The discoid figui'e is not a sufficient distinction from the genus Actinophrys ; 

 and, on the other hand, the softness of the integument, compared with the 

 lorica of Arcella, is not a generic distinction ; for the so-caUed lorica of the 

 latter genus is in many instances only a flexible integument. 



Cohn (Zeitschr. 1853, Band. iv. p. 262), after remarking on certain Acti- 

 nophiyean beings covered wdth adherent foreign particles of sand, Cyclo- 

 tella-sheRs, tfec, and surmising that such beings were no other than Diffluyice 

 engaged in the formation of a lorica, submits the opinion, in a foot-note, that 

 Trichodiscus Sol (Ehr.) is a similar organism, because Ehrenberg describes its 

 tentacles as proceeding from the middle of the body, which is often partially 

 coloured with brownish corpuscles. 



Trichodiscus Sol (Actinophrys Dis- I Amongst Confervas. Diam,, without 

 cvs,J).). — Depressed, almost flat, hyaline rays, 1-430" to 1-210". 

 or yello\\ash, with variable rays. The Perty, as already seen, retains this spe- 

 motion of this species is very sluggish ; cies with Actinophrys, with the name of 

 it often remains for a long- time inert. I A. Stella. 



Genus PODOPHRYA (XXIII. 34-37).— The members of this genus differ 

 from Actinophrys only in being stalked. Stalk single, not branched. Eh- 

 renberg described them as Enchelia devoid of vibratile cilia and teeth, with 

 spherical bodies, covered with setaceous tentacles ; having a truncated (direct) 

 mouth ; and in organization equivalent to Actinophrys, with a stiff stalk. 



PoDOPHRYA ovata (Alder). — Body 

 ovate, with a very slender and short 

 stem ; tentacles capitate, retractile, in a 

 single row, less numerous than in JSphe- 

 lota apiculosa, and forming a narrow disc. 

 Parasitic on Sertularice. 



P- pyriformis (Alder). — Body pear- 

 shaped, or rather campanulate, with a di- 

 stinct rim around the summit, and a sin- 

 gle circlet of delicate, capitate, retractile 

 tentacles; stem long and slender. Pa- 

 rasitic on Paludicella, and, milike the 

 preceding, an inhabitant of fresh water. 



These two species were first described 

 by Mr. Alder, along vnih Ephelota apicu- 

 losa, and were described in the previous 

 edition of this work, under the name of 

 " Alderia." Lately, however, Mr. Alder 

 wi-ote to inform us that this name had 

 been applied to a difterent class of ani- 



mals, and therefore could not be retained. 

 Dr. Strethill Wright has since studied 

 these beings, and distinguished one as 

 Ephelota apicidosa, and placed the other 

 two among Podophryce. Mr. Alder (A. 

 N. H. 1851, Y\\. p. 427) recognized their 

 relation to Acinetc?, and their afhnit}^ 

 to Campanularian Zoophytes, between 

 which and Infusoria he considered them 

 the most perfect link known. 



V. Jixa {Trichoda jixa, M. Actino- 

 phrys pedicelhda, D.). — Body spheiical, 

 turbid, whitish, with a diaphanous pe- 

 dicle slightly excised at the extremity. 

 The rays or tentacles are capitate at the 

 extremity, and equal in length the dia- 

 meter of the body. Ehrenberg states 

 that the seizing or catching power of 

 this animalcule is very interesting to ob- 

 serve. So soon as a quickly-vibrating 

 2 



