GENUS HEX A MIT A. 319 



first transferred to the stage of the microscope, they, like Polytoma, usually rush wildly 

 about the field, conveying the impression that they are entirely free-swimming. After a 

 short interval, however, their movements get less excited, and they finally affix them- 

 selves to the glass slide, or any neighbouring organic debris, by their adherent 

 posterior flagella, while the four anterior appendages are vibrated actively in the 

 surrounding liquid medium, in the manner indicated at PL XIX. Fig. 61. The 

 exact number, character, and point of insertion of the flagella may be readily 

 substantiated during this attached condition, though with even greater facility on 

 killing the little creatures by the application of a small drop of iodine or osmic acid. 

 The extreme flexibility of these animalcules is frequently manifested in both their 

 natatory and sedentary conditions, the body being frequently flexed to such an extent 

 that the anterior and posterior extremities almost touch. In the figures of Hexamita 

 intestinalis, recently published by Stein, two examples are represented as possessing 

 a delicate, denticulate, frill-like membrane on each side of the anterior border, one 

 of these, as represented at PI. XIX. Fig. 62, exhibiting in addition numerous elon- 

 gate papillose projections in the posterior region, which are pronounced in the 

 index to be merely adherent Bacteria. No such frill-like border could be detected 

 in any of the examples examined by the author, and it would seem highly probable 

 that both this structure and the Bacteria-like appendages represent peculiarly modi- 

 fied pseudopodic expansions of the body-sarcode of the animalcule preparatory to 

 the assumption of an encysted state. Similar slender papillose pseudopodia are 

 shown in this volume to be emitted under like circumstances by the zooids of 

 Codosiga botrytis and Cephalothamnium c&spitosa. The young of this species, 

 according to Stein's figures, possess only two anteriorly inserted vibratile flagella, 

 while the general contour of the body is more attenuate than that of the adults. 



Among the numerous examples recently examined by the author, zooids were 

 not unfrequently observed, in which the posterior region was distinctly cleft or 

 bifurcated, after the manner of the succeeding species. This circumstance, added 

 to the fact of the identity of the habitats of the free-swimming H. inflata and the 

 Amphibia that harbour H. intestinalis, not unnaturally raises a doubt as to whether 

 these two presumed distinct types may not ultimately prove to be free-swimming, 

 and endoparasitic phases of the same specific form. 



Hexamita inflata, Duj. PL. XIX. FIGS. 56-59. 



Body oblong or subquadrangular, emarginate or bifid posteriorly, 

 plastic and changeable in form, varying from one and a half to two or three 

 times as long as broad, the two caudal trailing flagella produced as tail-like 

 prolongations of each limb of the posterior bifurcation, the four anterior 

 vibratile flagella originating close to one another in the centre of the 

 anterior border ; contractile vesicle anteriorly located ; endoplast sub- 

 central. Length 1-2500" to 1-1200". 



HAB. Pond water with decomposing organic matter and in vegetable 

 infusions. 



Independently of its distinct habitat, this species is to be distinguished from the 

 preceding form by its broader contour and the conspicuous emargination of the pos- 

 terior region. It has recently been figured by both Stein and Biitschli, and has also 

 been obtained by the author from both marsh-water and from an infusion of decaying 

 flowers, its companions in each instance being Trepomonas agilis, and in the latter 

 one also Vorticella infusionum. Like Hexamita intestinalis, it has been frequently 

 observed to affix itself by the two caudal flagella, the anterior appendages being 

 meanwhile deployed and vibrated actively in the surrounding water, with the 

 apparent object of drawing suitable food-particles within reach of the body. The 

 animalcules under this temporarily affixed condition were found on several occasions 



