1884.] 



MICROSCOPICAL JOURNAL. 



125 



sile, flexible and contractile, five to 

 six times as long as broad, widest 

 centrally, thence gradually narrow- 

 ing to the origin of the anterior neck- 

 like prolongation which is not con- 

 spicuously distinguished from the 

 body, and to the posterior extremity ; 

 somewhat gibbous and bearing on the 

 right-hand margin a series of about 

 eight equi-distant, hemispherical ele- 

 vations, each of which contains sev- 

 eral trichocy sts ; dorsal s u r f a c e 

 smooth and naked, the ventral cili- 

 ated and longitudinally furrowed ; 

 neck-like prolongation equalling 

 about one-third the length of the en- 

 tire body, its extremity curved to- 

 ward the right ; tail-like portion short, 

 flat, obtusely pointed ; food particles 

 and endoplasmic granules not scat- 

 tered throughout the neck, tail or lat- 

 eral borders of the body ; trichocysts 

 very numerous, obliquely set along 

 the left-hand border of the neck and 

 body, continued around the margin of 

 the tail-like region, and contained 

 within the boss-like elevations of the 

 right-hand border ; contractile vesi- 

 cle single, posteriorly placed near the 

 dorsal surface, in advance of the tail- 

 like prolongation, and formed by the 

 coalescence of several small vacuoles ; 

 nuclei two, ovate, sub-centrally lo- 

 cated. Length of extended body, 

 j-^inch. Habitat. — Standing water. 



The oral aperture has not been ob- 

 served. Careful examination has dis- 

 covered no vacant spot between the 

 multitudinous trichocysts which 

 might be occupied by that orifice ; the 

 inference may therefore be that the 

 mouth is subterminal, as with the 

 preceding species. 



The infusorian is capable of con- 

 traction to about one-third of its ex- 

 tended length, when it presents an 

 irregularly ovate aspect, the right- 

 hand border being coarsely crenated 

 by the approximation of the hemis- 

 pherical protuberances. Figure 8 

 shows it ventrally in optical section, 

 extended and magnified 300 diameters. 



Petalomonas disomata^ sp. nov. 

 (Greek, disotnatosy double bodied.) 



Body ovate, more or less pyri- 

 form, depressed, widest and rounded 

 posteriorly, the anterior extremity 

 obtusely pointed, both the dorsal and 

 ventral surfaces having a longitudinal 

 groove or channel extending in or 

 near the median line from the apex 

 to the posterior extremity ; oral aper- 

 ture conspicuous ; flagellum some- 

 what longer than the body, arising 

 from a point on the ventral surface a 

 short distance back of the anterior 

 apex, directed rigidly in advance, the 

 distal extremity only vibrating ; con- 

 tractile vesicle single, in the anterior 

 body half near the median groove ; 

 nucleus on the opposite side some- 

 what f u r t h e r back ; parenchyma 

 transparent anteriorly, granular, and 

 semi-opaque with food particles pos- 

 teriorly. Length of body j^Vo inch. 

 Habitat. — The surface of decaying 

 leaves at the bottom of shallow 

 ponds. 



The movements of the animalcule 

 are directly forward in a straight line, 

 with sudden changes to the opposite 

 direction, the flagellum being fre- 

 quently held in contact with the slide 

 or other object traversed, and the 

 body obliquely elevated, the oral ap- 

 erture thus apparently gliding over 

 the ground in search of food, which 

 consists chiefly of minute refractive 

 particles, seemingly small starch 

 granules. Occasionally the hind 

 body has a green tinge by the incep- 

 tion, apparently, of chlorophyll 

 grains ; usually, however, the ani- 

 malcule is colorless. 



At times the dorsal and ventral 

 channels are indistinct, being repre- 

 sented by only a slight indication of 

 a depression ; in other individuals 

 the sulci are deep and disposed 

 slightly on one side of the median 

 line, thus dividing the body unequally. 



In figure 7 is shown the infusorian 

 in ventral aspect, magnified 1,000 

 diameters ; in figure 9 a transverse 

 optical diagrammatic section, exhib- 

 iting the double-bodied appearance 

 produced by the two medially dis- 

 posed channels. 



