GENUS DIPLOMITA. 289 



least one-half of the total bulk of this structure, imparting to it, by their dense 

 aggregation, the rich chestnut-brown or tawny hue characteristic of the entire organism, 

 as seen even with the unassisted vision. The interpretation of the nature and origin 

 of these minute coloured granules is undoubtedly to be found connected with the 

 phenomena of excretion, and of which they are as much the direct product as is the 

 branching stem or zoodendrium of Authophysa vegetans, described in a previous 

 page. In its more robust state of growth, the excreted elements in that species are 

 welded together so as to produce one tolerably homogeneous, longitudinally striate 

 stem ; but in its more weakly condition, or when the food-material supplied is not 

 sufficiently soluble, the excreted refuse is deposited and built into the substance of 

 the stalk as two distinct elements, partly mucous and partly granular. It is this 

 more abnormal condition, as seen in Authophysa, that represents the normal one 

 of Spougomonas, and apparently also that of the several previously-named Flagellate 

 genera in which the mucilaginous and granular constituents are as persistently 

 distinct. In Rhipidodendron and Cladomonas, however, the separate granular and 

 mucilaginous elements, while plainly visible in the external wall of the zoothecium, 

 are more closely amalgamated, and present an almost complete homogeneous 

 consistence in the interior or lining layer of each tubule, the structure in its integrity 

 thus acquiring that greater solidity which permits of its assumption of an erect 

 dendritic contour. 



The zooids of Spongomonas saccuhis were observed to divide by transverse fission, 

 the temporary retraction of the flagella and the lengthening and segmentation of the 

 ovate endoplast constituting the preliminary act to such duplicative process. 

 Sporular subdivision, as recorded of ^. mtesti)ium,\i2A not as yet been detected. The 

 distinction of this type from Spongomonas nvella, its apparent nearest ally, is mani- 

 fested, independently of the comparatively colossal proportions it attains, by the 

 crowded distribution of the monads within each lobe or saccular dilatation of the 

 compound zoocytium, those in the last-named type occupying each a separately 

 projecting chamber. 



Genus IV. DIPLOMITA, S. K. 

 (Greek, diploos, double ; mitos, thread.) 



Animalcules solitary, evenly ovate, attached by a thread-like retractile 

 ligament to the bottom of a simple, pedicellate, horny lorica ; flagella two in 

 number, similar in length and character ; the front margin not produced in a 

 lip-like manner; a rudimentary eye-like pigment-spot often present in the 

 anterior region ; no distinct oral aperture. Inhabiting fresh water. 



The as yet single known representative of this genus, while resembling Bicosoeca 

 in the form of the lorica and its mode of attachment within the same, exhibits in 

 the character of the flagella and general features of the contained animalcule, so 

 close a conformity to the zooids of Spongomonas and its allies, that it is here referred 

 to the same family group. 



Diplomita socialis, S. K. Pl. XVIII. Figs. 30 and 31. 



Lorica evenly ovate, about twice as long as broad, attached by a short 

 pedicle ; animalcules with two long terminal flagella of equal length, occu- 

 pying a little more than one-half of the cavity of the lorica, slightly exsert 

 from the aperture of this structure when extended; contractile vesicle 

 posteriorly located ; endoplast spherical, subcentral ; parenchyma trans- 

 parent, homogeneous ; a minute, eye-like pigment-spot situated near the 

 anterior extremity. Length of lorica 1-1675" ; colour pale brown, or amber 



Hab. — Pond water. 



