GENUS POLYTOMA. 301 



researches of this author establish the accuracy of Dujardin's original anticipation 

 that the animalcule possessed two flagella proceeding from the extremities of the 

 recurved lobate processes, although by Perty, Fresenius, and more recently by De 

 Fromentel, a single flagellate appendage only is reported. The figures given by these 

 last-named authorities, representing this form as caliper-shaped or bifid posteriorly, 

 with a single median anterior flagellum, is now shown to be an imperfect interpre- 

 tation of the lateral view given at PL XIX. Fig. 10. By Diesing Trepomonas 

 agilis is described as possessing a terminal oral aperture ; but Biitschli, while 

 noting the presence in the endoplasm of enclosed foreign particles, entirely failed to 

 discover the existence of such a structure. Under these circumstances it seems 

 desirable to refer this type, at all events provisionally, to the Pantostomatous section of 

 the Flagellata, the food-particles observed being probably incepted at any point of 

 the periphery. A circulation or cyclosis of the inner substance of the endoplasm is 

 recorded of this form by Biitschli, and has been witnessed by the author, which 

 corresponds broadly with that which obtains in the higher Ciliate type Faramecium 

 bursaria. Two animalcules joined to one another posteriorly by a slender, fila- 

 mentous extension of the body-sarcode, representing an advanced phase of the 

 process of longitudinal fission, was observed on one occasion. The correspondence 

 that subsists between the contour of this type, as seen in lateral aspect, Fig. n, and 

 the fission-stage of Ancyromonas sigmoides (see PL XIII. Figs. 51 and 52), is highly 

 remarkable. 



Stein, in his recently issued volume, gives a very exhaustive series of illustrations 

 of the polymorphic contours presented by Trepomonas agilis under varying conditions 

 of attitude or flexure, the more important of which are here reproduced. The 

 young of this type are, in accordance with the same authority, provided with three 

 or four long, slender flagella, presenting under such conditions the appearances 

 delineated at PL XIX. Figs. 13 and 14. 



Fam. XI. POLYTOMID-2B, S. K. 



Animalcules symmetrical, free-swimming or temporarily adherent, 

 illoricate, but with a more indurated membraniform cuticular envelope ; 

 flagella terminal, two in number, of equal size ; no distinct oral aperture ; 

 multiplying by endogenous subdivision. 



GENUS I. POLYTOMA, Ehrenberg. 



Animalcules biflagellate, free-swimming or temporarily adherent, more or 

 less ovate, persistent in shape, possessing a distinct investing membrane; 

 flagella of equal length, projecting from the anterior extremity ; contractile 

 vesicles and endoplast conspicuous, inhabiting water containing decomposing 

 animal matter. Increasing by endogenous multiple fission and by the pro- 

 duction of macro- and micro-spores. No distinct oral aperture. 



The type-form of this genus, the Polytoma uvella of Ehrenberg or Monas iiva of 

 Miiller, is evidently identical with the so-called " biflagellate or acorn-monad " 

 figured and described by Messrs. Dallinger and Drysdale in the ' Monthly Micro- 

 scopical Journal' for December 1874. A considerable difference of opinion has 

 existed as to whether Polytoma, as represented by this type, should be rightly referred 

 to the animal or vegetable kingdom, the balance of evidence being now, however, 

 entirely in favour of the first alternative. There is no secretion of chlorophyll 

 within the endoplasm as in the ordinary phytozoa, and the investing membrane 

 refuses to become blue under the action of iodine, as it would if composed of 

 cellulose. Ehrenberg further reports that the animalcules will ingest coloured 

 matter, such as indigo, and figures artificially fed examples in his work. This last 

 circumstance, combined with the constant presence of conspicuously developed 



