SCIENCE-GOSSIP. 



37 



BRITISH INFUSORIA. 



By E. H. J. Schuster, F.Z.S. 



Part II. — Flagellata Pantostomata. 



(Continued from page ii.) 



npHIS order contains the lowest and least 

 specialized forms of the flagellate Infusoria. 

 The oral aperture is quite indefinite, and in those 

 cases where solid particles of food matter are 

 ingested, any part of the body cavity performs the 

 function of mouth. It is in this way that the 

 ordinal name, Pantostomata, which means animals 

 who are all mouth, is derived. Locomotion is 

 effected, as in the Eustomata, by means of vibratile 

 flagella. Mr. Saville Kent's classification is based 

 on the number of these organs present, and by this 

 means are established three sub-orders, the Mono- 

 mastiga, the Dimastiga and the Polymastiga. 

 These possess, respectively, one, two and more 

 than two flagella for propulsive purposes. 



The most highly organized forms occur in the 

 last section, particularly in the family Lophomo- 

 nadidae. As these animals are for the most part 

 endoparasitic in habits, I am inclined to believe 

 that the absence of a definite oral aperture is due 

 to degeneration, and that the forms in question are 

 derived from eustomatous species. In this case, 

 of course, they ought not to be included in the 

 order Pantostomata. Among the lower families, 

 the individuals are for the most part irregular and 

 inconstant in shape. The species shade insensibly 

 into one another, and in many cases are probably 

 only developmental phases of other Infusoria 

 spores of algae, etc. Taking these things into 

 consideration, only those species whose life- 

 histories have been thoroughly worked out can be 

 considered as satisfactorily established. 



The following are descriptions of some mode- 

 rately distinct and widely distributed forms. 

 Whether they all deserve specific names of their 

 own or not is an open question. It may be 

 answered by any energetic person who thoroughly 

 investigates the details of their lives. 



Sue-Order Monomastiga. 



Family Monadidae, Ehrenberg. — "Animalcules 

 naked or illoricate, entirely free - swimming ; 

 flagellum single terminal, no distinct oral aperture, 

 ail endoplast or nucleus and one or more con- 

 tractile vacuoles usually present." 



Monas varians Dujardin, is exceedingly plastic 

 and variable in form, its most regular contour is 

 oblong, tapering slightly towards the anterior 

 extremity, at which the flagellum has its origin. 

 The body substance is soft and glutinous. A 

 sub-central and spherical nucleus and one con- 



tractile vacuole are present. The length is from 

 32 to 40 microns, the flagellum is about twice 

 as long. 



This animal may be found in ditch-water ; it 



Fig. 1^.— Monas varians ( x 600). 



Some of the various shapes which the animal assumes are 

 shown here. 



prefers those ditches which have trees overhang- 

 ing them. It was discovered by Dujardin on 

 November i8th, 1838, in some water which he 

 had kept for eight days after having taken it from 

 a roadside rut on the north side of Paris. 



Monas raniulosa Stein, is elongate and sub- 

 cylindrical in shape ; it is widest at the posterior 

 extremity, and conical anteriorly. The peripheral 

 surface is sometimes produced into a number of 



Fig. n.— Monas ramulosa ( x 600). 



n, nucleus ; cv, contractile vacuole. 



(i) Condition with fingerlike processes protruded; (2) the 



same without them. 



finger-shaped lobes, not entirely unlike the pseudo- 

 podia of an Amoeba. The flagellum is about 

 the same length as the body, sometimes a trifle 

 longer, and springs from the anterior end. A 



