3 1 4 ORDER FLA GELLA TA-PANTOSTOMA TA. 



podic processes by the aid of which it is enabled to creep about after the manner of 

 an Amoeba. Messrs. Dallinger and Drysdale further add that when in this amoeboid 

 condition they rapidly devour such living or dead Bacteria as they may chance to 

 come across, ingesting them as Amoeba do at any point of their periphery. 

 The two rhythmically opening and closing so-called " eye-like spots " referred 

 to by these same writers as being constantly present at the anterior extremity 

 of the animalcules, evidently represent the contractile vesicles common to almost 

 all members of the Flagellata. Perty and Fresenius indicate the existence of a single 

 large vesicle only at its anterior end ; but the two, as shown by Messrs. Dallinger 

 and Drysdale, are situated so close to each other as to naturally appear as one only, 

 unless an extremely high magnifying power is employed. Perty's description 

 and illustrations of the process of longitudinal fission differ to a slight extent from 

 that reported by Messrs. Dallinger and Drysdale, he having observed on various 

 occasions that the four new flagella are developed before the partitioning into 

 halves of the original animalcule, and which is thus provided for a short interval 

 with eight of these appendages. The young of this species, as recently figured 

 by Stein, possess a very attenuate contour, as shown at PI. XIX. Figs. 47 and 48, 

 more closely resembling in this respect the adult form of Tetramitus dcscissus. 



Tetramitus descissus, Perty. PL. XIX. FIGS. 49 AND 50. 



Body elongate, slightly curved, conical or wedge-shaped, plastic and 

 somewhat variable in form, the posterior extremity mostly tapering and 

 pointed, sometimes obtusely rounded ; the anterior half of the body 

 obliquely truncate or excavate on its concave or ventral side ; flagella 

 subequal, slender, inserted close to one another at the anterior margin 

 of the frontal excavation ; contractile vesicle single, located near the 

 posterior extremity ; endoplast central, spherical. Length of body 

 1-1800". HAB. Stagnant water with decomposing organic matter. 



This animalcule, originally described by Perty under the above title, is apparently 

 identical with the flagellate form recently investigated by O. Biitschli, and referred by 

 him, while retaining Perty's specific name, to the genus Pyramimonas. There are 

 nevertheless one or two points in Biitschli's account which do not exactly correspond 

 with Perty's figures and description, though such differences as exist may be possibly 

 attributable to mere local variation. Thus the flagella, while described by the earlier 

 authority as being equal to or longer than the body, are represented by Biitschli as 

 only half that length. The obliquely truncate anterior border bearing these flagella 

 is likewise described and figured by the same authority as extending backwards on 

 the ventral side to a much further distance than is shown by Perty. 



These distinctions, if further substantiated, may necessitate the future introduction 

 of two separate specific titles in place of the one here employed. The sarcode 

 substance of this variety is apparently more plastic and liable to variations of outline, 

 under normal conditions, than that of Tetramitus rostratus. No details have yet 

 been recorded respecting the phenomena of reproduction. Representations of this 

 species closely corresponding with those given by Biitschli are included in Stein's 

 recently published volume. 



Tetramitus sulcatus, Stein. PL. XIX. FIGS. 26 AND 27. 



Body obtusely pyriform or subcordate, widest and rounded anteriorly, 

 tapering towards and bluntly pointed at the posterior extremity, about one 

 and a half times as long as broad ; a deep groove traversing the entire 

 length of the centre of the ventral side and imparting to the posterior 

 extremity, as seen from beneath, a bilobate contour; flagella four in number, 



