2QO ORDER FLAGELLATA-PANTOSTOMATA. 



The lorica in this species so closely resembles that of Bicosceca lacustris, that when 

 empty, except for its larger size, it might be easily mistaken for it. The structure of 

 the enclosed animalcule is, however, altogether distinct. In place of the one Jong 

 and one short flagellum, there are here two long, equal-sized flagella, which lash the 

 water vigorously in every direction, instead of being extended rigidly in an arcuate 

 form with the extreme point alone vibrating, as obtains in the single long appendage 

 of Bicosceca. There is likewise no distinct lip-like projection or rostrum, as in that 

 type, the anterior border being evenly rounded. Where found, this animalcule 

 usually occurs in considerable numbers, completely covering the filaments of 

 Conferva or other aquatic objects, as shown in PL XVIII. Fig. 31. The 

 colour of the lorica in Diplomita is deeper than has as yet been observed in any other 

 representative of the Pantostomatous group, presenting usually in adult examples a 

 pale brown or amber hue. This circumstance may be cited as additional evidence 

 in indication of its near affinity to the generic forms with which it is here corre- 

 lated, but which in place of secreting separate loricae, build up similarly coloured 

 zoothecia or zoocytia. In all the examples so far examined, a bright spot, cor- 

 responding apparently with the so-called eye-speck of Euglena, Dinobryon, and other 

 Flagellata, was conspicuous towards the anterior extremity. This type was first 

 figured and briefly described by the author under the title of Bicosceca svciatis, in the 

 ' Monthly Microscopical Journal' for December 1871. 



Fam. IX. HETEROMITIDJE, S. K. 



Animalcules naked, free-swimming or temporarily attached ; flagella 

 two in number, the more anterior appendage, " tractellum," locomotive and 

 vibratile, the posterior one, " gubernaculum," usually trailing and adherent ; 

 no distinct oral aperture. 



The representatives of this family correspond closely in their general form, 

 habits, and character of the flagella with those of the Stomatode Anisonemidae, but 

 differ from them owing to the total absence of a distinct oral aperture, food-ingestion 

 being accomplished at diverse points of the periphery. The appropriate titles of a 

 "gubernaculum" and "tractellum," proposed respectively by Professors H. James- 

 Clark and E. Ray Lankester for the distinction of the peculiar modified trailing 

 flagellum and the ordinary vibratile appendage characteristic of the Heteromitidae 

 and other Flagellata, are here cordially adopted. A fuller reference to this subject 

 is made in the account given hereafter of the family Anisonemidae. 



GENUS I. HETEROMITA, Dujardin. 



Animalcules free-swimming or temporarily attached, ovoid, globular, or 

 elongate, plastic and changeable in shape, having no differentiated cuticular 

 investment ; flagella two in number, originating close to each other at the 

 anterior or antero-ventral extremity of the body, the foremost, tractellum, 

 directed in advance and constantly vibrated, the more posterior one, guber- 

 naculum,usually trailing, or adherent by its distal extremity ; food ingested 

 at any portion of the periphery, possessing no distinct mouth. Inhabiting 

 fresh and salt water, very abundant in animal and vegetable infusions. 



Dujardin instituted this genus for the reception of those flagellate forms which, 

 while agreeing with Heteronema and Anisonema in their external contour, are to be 

 distinguished from them by the absence of a distinct cuticular investment. By 

 many later writers this distinction has been considered insufficient for generic sepa- 

 ration. A prolonged and careful investigation of numerous representatives of this 

 genus has, however, enabled the author to point out a second and even more important 

 correlative differentiation. Reference is here made to the ingestive functions, which 



