122 



THE AMEKICAN MONTHLY 



[July, 



late. Length of body, -g-^ inch. 

 Habitat, the surface of decaying 

 leaves at the bottom of shallow pools. 



This infusorian resembles Lemba- 

 dion and will probably follow it in a 

 scheme of classification. The move- 

 ments of both are also similar. When 

 first placed on the microscope slide 

 they swim backwards by rapid revo- 

 lutions on their long axes, the mo- 

 tion probably being caused by the 

 vibrations of the adoral membrane. 

 When quietly searching for food they 

 swim evenly forward or in irregular 

 circles. Hymenostoma differs from 

 Lembadion in the posterior, ventral 

 position of the mouth, the greater 

 length of the adoral cilia, the abruptly 

 narrowing membrane, the double 

 contractile vesicle, and the greater 

 number and sinistrally directed set£e 

 of the posterior extremity, four being 

 the usual complement with Hymen- 

 ostoma. 



In its food-habits Hymenostoma 

 is omnivorous, taking diatoms and 

 animalcules of comparatively enor- 

 moiffe size, often leaping from side to 

 side as if eager to seize its prey. 

 The food particle is often somewhat 

 larger than the oral aperture, so that 

 the entrance becomes blocked and 

 the captive not at once engulfed. 

 Just how this engulfing process is 

 performed I have not learned. Nei- 

 ther the adoral cilia nor the oral 

 membrane seem to take active parts. 

 The cilia on the left-hand margin of 

 this depression are seen to be very 

 fine and dense when the animalcule 

 has been killed, having, after death 

 by iodine, the property of falling 

 from their attachment as a continuous 

 fringe. At other times they are rare- 

 ly visible, on account of their rapid 

 vibrations. The mouth is also often 

 very inconspicuous until the sur- 

 rounding membrane is extended and 

 vibrated. The food, after passing 

 this opening, invariably takes a posi- 

 tion in the left side of the body. 



The rate of pulsation of the smaller 

 contractile vesicle is not constant. 

 When the infusorian is multiplying 



by transverse fission the contractions 

 are at the rate of twenty-eight per 

 minute ; at other times the movement 

 is as snapping, but at longer intei'vals. 



The infusorian is represented in 

 figure I, magnified 600 diameters. 



Trachelophyllum vestitum, sp. 

 nov. 



Body elongate flask-shaped, much 

 flattened, very extensile and elastic, 

 the length from four to five times the 

 breadth ; neck somewhat fusiform, 

 about one-half of the body in length, 

 the apical constriction truncate, some- 

 what dilated distally ; the entire sur- 

 face, except the apical constriction, 

 invested by a mucilaginous, struc- 

 tureless or finely granular coating 

 whose depth equals about one-third 

 the entire length of the cuticular cilia, 

 the latter being fine, thinly clothing 

 the body in longitudinal rows, their 

 action somewhat independent and ir- 

 regular, only that portion of each 

 cilium vibrating which extends be- 

 yond the mucilaginous investment ; 

 pharyngeal tract distinct, finely stri- 

 ate longitudinally ; nuclei two, ovate, 

 one nodule located in the anterior, 

 the other in the posterior body half; 

 contractile vesicle single, posteriorly 

 placed, quickly forming after systole 

 by the union of several vacuoles which 

 often become visible just previous to 

 the pulsation ; anal aperture postero- 

 terminal ; trichocysts ( .'') abundant, 

 acicular, scattered and collected in 

 fascicles. Length of body y^ inch. 

 Habitat. — The surface of submerged 

 and v^^ater-soaked objects at the bot- 

 tom of shallow ponds. 



The body contains needle-shaped 

 objects scattered throughout its sub- 

 stance and collected in obliquely-dis- 

 posed bundles, deeper, apparently, 

 than the cortical layer. They may 

 be trichocysts, but their foi'm and the 

 action of the light suggest that they 

 may be crystals. They closely resem- 

 ble the acicular raphides so abundant 

 in Lemna^ Tradescantia., and other 

 common plants. The solution of tan- 

 nic acid in glycerin has no visible 

 effect upon their position. Figure 2 



