432 ORDER FLAGELLATA-EUSTOMATA. 



Diplomastix caudata, Duj. sp. Pl. XXIV. Figs. i-io. 



Body variable in form, gibbously ovate, sometimes rounded, but more 

 usually tapering and bent obliquely upwards posteriorly, the anterior 

 extremity sharply pointed or rostrate, curved towards the ventral aspect ; 

 flagella slender, subequal, exceeding the body in length, inserted close 

 to each other at the apex of the rostrate process; contractile vesicle 

 located near the anterior extremity ; endoplast subcentral ; endoplasm 

 transparent, finely granular. Length 1-1500" to 1-500". 



Hab. — Pond water and organic infusions in both salt and fresh water. 



This species is figured without an accompanying description, in Stein's recent 

 volume,* under the title of Bodo caudata Stein, and with the associated synonym 

 of Ainphimonas caudata of Dujardin, a type again which is regarded by this last- 

 named authority as probably identical with the Bodo saltans of Ehrenberg. The 

 present author agrees with Stein in the recognition of this Ehrenbergian species 

 as a totally distinct form, and has arrived at the conclusion that there are 

 no less than three specific types closely resembling in general aspect the one 

 now under consideration, but which exhibit under more minute examination easily 

 apprehended distinctive features. All of these occur abundantly in hay and other 

 vegetable infusions, and have recently formed the subject of special investigation. 

 The present type, D. caudata, may be at once recognized by its larger size and 

 movements in the water, which consist chiefly of steady progress forwards in a 

 straight line for a more or less considerable distance, the rostrum directed down- 

 wards and rooting as it were among the organic debris, while the body sways to 

 and fro with a rapid vacillating or hitching action, such mode of locomotion is quite 

 distinct from the leaping or constantly reversed or tacking motion of the two smaller 

 types next described under the titles of Diplomastix affiiiis and D. saltans. Com- 

 pared with this last-named form, the contractile vesicle is also found to occupy an 

 exactly inverse position. 



The more conspicuous individual diversities of contour exhibited by the 

 present species are amply illustrated in the accompanying figures ; it is at the same 

 time worthy of remark that the author has found the shorter and posteriorly rounded 

 shape, PI. XXII. Fig. i, connected always with the earliest appearance of this 

 form, the more or less attenuate caudal prolongation, as shown at Figs. 2 and 3, 

 not making its appearance until the third or fourth day after the advent of the 

 animalcule in any quantity upon the field. This attenuate extension of the posterior 

 extremity would seem in the present type to take the place of the more irregular 

 pseudopodic processes, emitted mostly from the same region, in many Pantosto- 

 matous forms antecedent to the act of coalescence or encystment. Both of these 

 phenomena have been abundantly observed, as also the breaking up of the encysted 

 zooids into four or eight oval macrospores which shortly develop flagella and assume 

 the form and characteristic movements of their parents. It was also found that the 

 macrospores so produced were plentifully developed on the dried hay when first 

 placed to macerate (see PI. XL Fig. 2 c), lying scattered in little heaps, without 

 any common investing envelope, among the ridges and sinuosities of the surface 

 of the separate blades or stalks. The motile zooids derived from these spores 

 did not make their appearance until the fourth day of maceration, and remained 

 then for upwards of a month as one of the most abundantly represented types 

 in the infusion, sometimes crowding the field of view to the exclusion of all other 

 forms. 



By Stein this animalcule is figured as possessing a distinct tubular oral aperture 

 situated immediately beneath the recurved rostrum. Athough the inception of 

 food was observed at this point, the author has not yet succeeded in detecting any 



* 'Infusionsthiere,' Abth. iii., 1878. 



