OF THE MONADINA. 



497 



B. diclymm. — Generally constricted 

 about midway, tail short. 1-9600". 



B. saltans. — Very small ; body with 

 ample ventricles ; tail short. This 

 creature, most probably from its small 

 size, has been mistaken for Miiller's 

 Manas Termo ; but its brisk leaping move- 

 ment will sufficiently distinguish it. 

 1-1200". 



B. grandis. — Oblong ; vesicles ample ; 

 tail rigid, setaceous, affixed to the abdo- 

 men. In stagnant water. 1-864". 

 Lachmann states that an animal which 

 was probably Bodo grandis, but might 

 have been an Astasia, devoured Vibrio 

 of two to four times its own length, 

 and in this way acquired the most 

 extraordinary forms j the mouth was 



close to the insertion of the flagellum. 



B. ostrecB (Pritchard). — Globular; the 

 anterior three-fourths occupied with ve- 

 sicles, the rest hyaline ; length of tail 

 four times the diameter of body. This 

 active creature was discovered in the 

 liquor of an oyster, swimming freely 

 among the ova (Sept. 1834). Diam. 

 1-2000". 



B. ? Mastix (Ehr.). — Obovate, turgid, 

 smooth; terminal seta flexuose, acute, 

 exceeding some two or three times the 

 length of the body. Length 1-48"' to 

 1-30"', with the filament 1-20"'. The 

 filament trails behind ; motion slow, not 

 leaping. This is the largest fonn of Bodo 

 observed by Ehrenberg. Fomid about 

 Sphagnum. 



The following genera, named and described by Dujardin, are introduced 

 into his family Monadina : — 



Genus CYCLIDIUM (D.) (XXVI. 14, 15).— Body discoid, compressed, or 

 lamelliform, scarcely variable ; the filament thicker and more rigid near the 

 base than that of Manas, the free extremity only being moved. 



This genus is as yet but artificial, and indeed provisional ; for true Monads 

 perfectly developed may possess a filament with a thicker base, and, again, 

 the constant outline of the body may be the consequence of the presence of 

 an integument — in which case the animalcules in question vrould be referable 

 to the family Thecamonadina. Movement slow and uniform. 



It is to be regretted that Dujardin uses this generic name, as Ehrenbei^ 

 previously employed it to designate certain ciliated animalcules which cor- 

 respond but partially with those of Dujardin. Indeed this naturalist ob- 

 serves that " the genus CycVidlum (Ehr.) contains Monads also, and very 

 probably some of those to which I have applied the same ' generic ' name." 



Cycltdium nodulostim (Duj.). — 

 Flattened, discoid, with rows of nodules 

 and vacuoles; movement extremely 

 slow. Length 1-5200". In water from 

 the Seine. 



C. ahscissum (Duj.) (xxvi. 15). — 

 Membranous, lamelliform, truncated 

 posteriorly; filament rigid; movement 

 slow, regular. 1-1040". 



C. crassum (Duj.). — Oval, thick, and 

 rounded ; filament thickened at its base 

 and rather sinuous ; movements more 

 active, zigzag. 1-1090". Length of fila- 

 ment 1-600". 



C. distortum (Duj.) (xxvi. 14) ( = 

 Spiromonas voluhilis, Perty). — Oval, flat. 



nodular, irregularlv bent, with a tumid 

 border. 1-1800" to 1-800". 



^'This species is perhaps only one phase 

 of development of Monas Lens ; it was 

 found in Seine water kept during three 

 months. When young it has the form 

 of a disk, with a tumid and nodular 

 margin ; when, however, it has grown 

 larger, it becomes twisted upon itself, 

 and its movements irregular. Some in- 

 dividuals offered a certain affinit}- wath 

 the Trepomonads, which favours the 

 opinion already advanced, that the ma- 

 jority of the Monadina are but modifica- 

 tions of one or of several types." 



Genus CERCOMONAS (D.) (XVIII. 11, 12, 20, 22, 23).— Body rounded 

 or discoid, tubercular, with a posterior variable process in the form of a tail, 

 of greater or less length and fineness. 



The Cercomonads differ from the Monads by the posterior prolongation, 

 which serves, by the adhesion of its extremity, as a point of support : it occui's 

 either as a very fine thread or contracted into a small tubercle ; it is some- 

 times nearly as fine as the anterior filament, and susceptible of an undulatory 



2k 



