OF THE MONADINA. 



493 



defined by him : — " animals globular or ovoid, having a single flagelliform fila- 

 ment, and living aggregated in spherical masses, freely moving about in the 

 liquid." He ftu'ther observes that isolated individuals are not at all distinguish- 

 able from simple Monads, that there is no good reason to suppose them to live 

 alternately isolated and in masses — a circumstance therefore which cannot, 

 according to Ehrenberg's statement, be employed to distinguish them from 

 Polytoma. 



Busk describes an early stage of development of Volvocc Splicer osir a as 

 constituting *' a species of the genus Uvella, or of Syncrypta, Ehrenberg " 

 {M, T. vol. i. p. 40). Again, Cohn (on Protococcus, Bay Soc. 1853, p. 559) 

 makes one of the multiform phases of development of Protococcus pluvialis, 

 " when the zoospore is divided into thirty- two segments," equivalent to a 

 Uvella or Syncrypta. 



Perty, in his account of Uvella virescens, denies the existence of a common 

 envelope, stating that when the water evaporates from around a specimen, 

 the coveiings of each individual corpuscle coalesce, and give rise to the appear- 

 ance of a general investment around them. He adds, moreover, that at 

 times the corpuscles are green, with a clear central stripe ; at others, hyaline 

 with a distinct green border, and some scattered specks ; and at others, again, 

 hyaline throughout. 



Dujardin describes only two species, viz. U. virescens, and U. rosacea = U. 

 Glaucoma (Ehr.). Perty contributes to the list U. stigmalica. 



U^^LLA virescens (Volvox Ulva, M.). 

 — Ovate, coloiu: green, occurs in dense 

 clusters amongst Confervas and Lemnse. 

 1-2000"; diam. of cluster 1-280." 



U. Chamcemorurn. — Smaller than the 

 preceding one. In water-butts. 

 1-2880"; diam. of cluster 1-570". 



U. Uva. — Has indistinct vesicles, and 

 is very small. In stagnant water. 

 1-4800"; diam. of cluster 1-960". 



U. atomus (3Ionas atomus, M. Lens et 

 Volvox socialis, M.). — Voracious, with 

 large vesicles. 1-6900" to 1-3406"; 

 diam. of cluster 1-1150". 



U. Glaucoma (Volvox socialis, M.). — 

 Oval, inclining to conical ; as it advances 

 in age the posterior extremity is attenu- 

 ated, and an elongated outline is assumed. 

 Hyaline, with large vesicles, and two 

 evident filaments : individuals loosely 

 aggTegated. In 1831, Ehrenberg first 

 observed a vibration at its anterior part, 

 and its reception of coloured food. In 

 1835, he discovered ^vithin the body of 

 this minute creature some g-reen Monads 



which it had swallowed. When fed on 

 indigo, as many as twelve vesicles were 

 filled, and it was sometimes seen to void 

 little blue particles, like imdigested 

 matter, from its mouth. With a power 

 of 800 diameters, a great number of small 

 colourless gi-anules, which he called ova, 

 were discerned lying between the nutri- 

 tive sacs. Fission both ti-ansverse and 

 longitudinal (xviir. 3, 4 : figm'es mag- 

 nified about 350 diameters). In water- 

 butts. 1-2300" to 1-2350"; diam. of 

 cluster 1-430". 



U. Bodo. — Eounded in front, attenu- 

 ated posteriorly; colour a beautiful 

 gi'een. In stagnant water. 1-4030" to 

 1-3450"; diam. of cluster 1-2350". 



U. stigmalica (Perty). — Coi-puscles of 

 a imiform sea-green colom* ; each with 

 a very fine red stigma. They are also, 

 somewhat broader than those of U. 

 virescens, and have a more decidedly 

 hyaline and apparently crenidated enve- 

 lope. At Berne much rarer than U. 

 virescens. 



Genus MICPtOGLENA (XYIII. 6).— Characterized by the presence of a 

 minute red eye-like speck at the anterior part of the body. In other respects 

 the species resemble true Monads, ha\dng a very delicate filament, no pro- 

 jecting Hps and tail, and swim in the direction of the long axis of the body. 

 They multiply by complete self- division. Two species only are known — the 

 one yellow, and the other green. 



MiCROGLENA punctifera (Unchelys Eye-speck red with a blackish central 

 punctifera, M.). — Yellowish, oval, or al- spot. Among slimy- water plants. 1-620". 

 most conical ; posterior extremity acute. M. monadina. — Of a beautiful green : 



