292 ORDER FLA GELLA TA-PANTOSTOMA TA. 



that within the course of only a few hours the entire field of the microscope, as 

 supplied from the most minute dipping, was found crowded with adult zooids corre- 

 sponding in form, size, and structure with the terms of the foregoing diagnosis. 



In their most characteristic adult state the animalcules of Heteromita lens are 

 normally subspherical or peach-shaped, as represented at PI. XV. Fig. i, but are 

 subject to considerable individual variation. An ovoid form with a somewhat nar- 

 rower anterior extremity (Fig. 2), on the symmetrical side, and an irregular, almost 

 amcebiform contour (Fig. 3) on the unsymmetrical one, represent the most constant 

 departures from the typical subspheroidal shape that have to be recorded. The 

 greater portion of these monads were to be seen, as soon as the excitement ensuing 

 upon their transference to the glass slide had subsided, temporarily attached, or 

 as it were anchored, to the glass or vegetable debris through the medium of the 

 hinder flagellum, or gubernaculum, and upon which the body oscillated, as though 

 on a pendulum, through the constantly vibratory action of the anterior appendage. 

 Many others were, however, swimming freely in the water, in some instances trailing 

 their posterior or guberaaculate flagellum in the rear, and flourishing the anterior one 

 in advance, while in others both flagella were directed anteriorly, their joint vibratory 

 action assisting in the task of locomotion. These last-named examples, however, 

 would appear to represent animalcules which had either passed or not yet arrived at 

 their complete development. Division by longitudinal fission, as also the coalescence 

 or fusion of the adult monads (Figs. 7 and. 8), were frequently observed, likewise the 

 subsequent encystment and breaking up of the intimately amalgamated zooids into 

 minute spores corresponding precisely in form and size with those from which, 

 as already shown, they originally sprang. In addition to this genetic mode of re- 

 production, multiplication by the simple encystment and splitting into four, eight, or 

 sixteen segments or macrospores of the single zooids, was likewise authenticated, 

 each such subdivided portion possessing two flagella, and, except for its more minute 

 size, corresponding entirely with the parent animalcules at the time of its liberation 

 into the surrounding water; the more conspicuous features of this reproductive 

 process are represented at Figs. 15-17 of the same plate. Investigations pursued 

 simultaneously with the vegetable material of a like nature macerated in sea-water 

 instead of fresh, were attended by a similar first arrival of a monad perfectly agreeing 

 in form and in its developmental cycle with the present species, excepting that the 

 size was slightly smaller and the endoplasm apparently a little more dense and 

 compact. This slight variation in size and consistence may be reasonably attributed 

 to the higher specific gravity of the fluid medium employed. The Heteromita gramdum 

 of Dujardin, characterized by its spherical granulate body and two equal, slender 

 flagella diameter 1-2250", hab. salt water is probably identical with this marine 

 variety of H. lens. 



A feature of interest relating to the life-history of the present species that 

 remains to be recorded, bears reference to the conduct of the animalcules under 

 conditions inauspicious to their well-being, and which may be regarded as a modi- 

 fication of the process of diffluence. Thus if confined in quantities between the 

 ordinary slide and cover-glass without a renewal of liquid medium, the oxygen 

 apparently gets insufficient to support life comfortably, the movements of the 

 animalcules grow weaker and more sluggish, and presently losing their capacity of 

 fixing or anchoring themselves by their trailing flagellum, they float freely in the 

 water, and are carried passively in whichever direction the capillary currents produced 

 by the evaporation of the water may set in. Sometimes the normal spheroidal or 

 ovate contour is retained for a considerable interval, but more usually the peripheral 

 wall appears to entirely lose its customary more firm consistence, and the whole 

 body-sarcode becomes projected in various directions, after the manner of ragged and 

 irregularly developed pseudopodia. As the animalcule drifts helplessly along, these 

 improvised pseudopodia often adhere tenaciously to the slide or other object, 

 arresting its further progress, the aspect manifested under such conditions being 

 represented at PI. XV. Fig. 4. With a renewal of fresh oxygenated water the 

 animalcules speedily reassume their pristine symmetry and activity, while by a 

 further withholding of this important element complete dissolution soon terminates 



