292 ORDER FLAGELLATA-rANTOSTOMATA. 



that witliin (lie course of only a few hours the entire field of the microscope, as 

 su|)i)lic(l from the most minute dipiiing, was found crowded with adult zooids corre- 

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



In their most characteristic adult state the animalcules of Ildcromitd 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 (l''ig. 2), on the symmetrical side, and an irregular, almost 

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

 dejxirtures from the ty[ncal subspheroidal shape that have to be recorded. The 

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

 upon their transference to the glass slide had subsided, tem])orarily attached, or 

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

 hinder ilagcllum, or gubernaculum, and U])on which the body oscillated, as though 

 on a peiiduluni, through the constantly vibratory action of the anterior ai)i)endage. 

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

 their posterior or gubernaculate ilagcllum in the rear, and nourishing the anterior one 

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

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

 would apjiear to rejn-esent animalcules which had either passed or not yet arrived at 

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

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

 subscciuent 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 sjirang. 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 jxirtion ])ossessing two llagella, 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 rejiroductive 

 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. I'his slight variation in size and consistence may be reasonably attributed 

 to the higher specilic gravity of the fiuid medium employed. The Hcfcroiiiita graniiliiin 

 of Dujardin, characterized by its si)herical granulate body and two equal, slender 

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

 variety of II. lens. 



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

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

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

 fication of the process of ditlluence. Thus if confined in ciuantities between the 

 ordinary slide and cover-glass without a renewal of liijuid 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 fiagellum, 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 sjiheroiilal or 

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

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

 botly-sarcode becomes projectetl in various directions, after the manner of ragged and 

 irregularly developeil jiseudopodia. As the animalcule drifts helplessly along, these 

 improvised pseuilopodia otten adhere tenaciously to the slide or other object, 

 arresting its further i)rogress, 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 



