OF THE HYDEOMORINA. 



603 



backwards or forwards indifferently, — 

 a circumstance adverse to the existence 

 of a filament at aU. 1-4800" to 1-2400". 

 Occm-s among Characeae. 



C. violescens. — Globular or elliptical, 

 transparent, and of a very pale violet 

 colour. It appears closely related to, al- 

 thoug-li not identical with, Monas vinosa 

 (E.). A filament could not be detected, 

 nor anv internal organs. At Bern, with 



Chara. 1-14,000" to 1-3000". These 

 coloured organisms form a colom-ing 

 layer on the mud at the bottom of 

 ponds, kc. The several species men- 

 tioned by authors referable to the genus 

 Chroinatium are — 3Ionas rosea, Morren ; 

 3Ionas Okenii, Weisse ; Monas vinosa, M. 

 eruhescens, 31. ochracea, and probably 

 31. prodigiosa and 31. gliscetis of Ehren- 

 berg's categorv. 



Gemis ACAELEUM. — Extremely minute, globular or elliptical ; perfectl} 

 transparent, without a trace of either external or internal organs. 



AcARi^UM Crepuscuhim = 3Ionas Cre- 

 pusculum (E.).— They swim rapidly past 

 each other, yet have nothing in their 



movements in common with those of the 

 Monads, but much rather with those of 

 the Bacterium Termo. 



Genus RHABDOMONAS (Fresenius). 



RHABDOMONAS incurva. — Stout, 

 elongated and cylindi-ical, slightly fal- 

 cate ; anterior extremity rather the 

 thicker; three prominent longitudinal 

 ridges ; green vesicles or granules occupy 

 the anterior half of the body ; progresses 



in a straight line, with a rotary or semi- 

 rotary motion on its long axis ; filament 

 li the length of the body. 1-60 to 

 1-50 millim. In stagnant water with 

 Confervse, &c. 



Genus GRYK/EA (Fresenius). 



Gryivi^a vacillans. — Colourless, hya- 

 line, compressed; when seen on its fiat side 

 its outline is circular, but on the narrow 

 side, pyriform, the posterior compressed 

 portion gradually thickening towards the 

 thicker front part. Advances with the 



thick end foremost, slowly revolving on 

 its long axis, with an oscillating motion. 

 Filament revealed by iodine. In stand- 

 ing water with Vallisneria in the Botanic 

 Gardens. It is, not unlikely, the same 

 being as 3Ionas urceolaris (Perty). 



FAMILY II.— HYDROMORINA. 



Characters. — Anenterous Polygastrica without appendages ; body uniform, 

 like that of the Monads, but, by reason of the spontaneous fission being im- 

 perfect, developed into a moniliform mass or polypary ; lorica absent. Indi- 

 viduals are at periods set free, which commence the same cycle of compound 

 development as the parent beings to which they oi-iginally belonged (Ehr.). 



The genera belonging to this family are Polytoma and Spondylomorum. 

 Poly to ma was described by Ehrenberg in the family Monadina ; but the sub- 

 sequent discovery of the genus Sjpondylomoriim, ha\ing the same general 

 characters, and differing like it from the other monads, led him to create this 

 new family Hydromorina to embrace the two. 



Perty has also recognized the propriety of detaching those Monadina which, 

 by the act of self-fission continuing incomplete, live together in compound 

 masses, and to designate them has invented the term " 3Ionadina Familiaria,^^ 

 equivalent in EngKsh to ''gregarious or aggregated Monadina." Under this 

 group, however, he has placed two other genera, which Ehrenberg has let 

 remain, somewhat unaccountably, among those Monadina liWng in an isolated 

 or free state. These other members of the Hydromorina or Aggregated 

 Monads are, Uvella and Anthophysa. Schneider {A. N. H. 1854, xiv. 326) 

 observes on the near alliance of Polytoma to Chlorogonhim eucJdormn. It 

 would seem that Cohn fails to find any truly distinctive characters between 



