Ill fiisoria from American Fresh Wafers. 109 



marginal seta3 referred to are evidently luxuriantly developed 

 dorsal hispid setaj. The absence of all trace of a supplemen- 

 tary ventral series of styles, together with the softness and 

 flexibility of the body, exclude it from Pleurotricha, while the 

 latter qualities and the absence of caudal setje exclude it from 

 Siylonychia^ which it otherwise somewhat closely resembles ; 

 and, finally, tlie interruption of the marginal setffi at the posterior 

 border refuses it admission among the species of Oxytricha, 

 and from Histrio it is further excluded not only by the poste- 

 rior interruption of the marginal setas, but by its soft and 

 elastic body. Its proper position is probably between Oxy- 

 tricha and Histrio. 



TacJiysoma mirabile^ sp. nov. (PI. III. fig. 7.) 



Body elliptical, less than four times as long as broad, the 

 extremities equally rounded ; frontal, ventral, and marginal 

 styles essentially as in T. agile^ but smaller and more setose ; 

 anal styles five, without tendency to form two groups ; peri- 

 stome-field arcuate, extending through about one fourth the 

 length of the ventral surface, reflected or right-hand inner 

 border none ; contractile vesicle spherical, near the centre of 

 the left-hand body-margin ; nucleus single, elongate, sub- 

 centrally located, with an elongate, laterally attached nucleo- 

 lus ; endoplasra granular ; dorsal hispid set£e long, most 

 conspicuously developed near the posterior extremity. Length 

 4^^ inch. 



Hah. Standing pond-water. 



This form bears a close resemblance to the first-mentioned 

 member of the genus, differing from it somewhat in size, but 

 most conspicuously in the remarkable nucleus and nucleolus. 

 The latter is so large and so closely resembles the nucleus 

 that the two might be considered a uniquely arranged double 

 nucleus, especially in certain individuals in which the nucleo- 

 lus has become slightly separated from its lateral attachment. 

 In none of the Hypotrichous Infusoria, so far as I am aware, 

 has a similar nucleus been previously observed. 



The movements of the animalcule are rapid and erratic. 

 The body is frequently observed to be laterally curved, which 

 region then becoming somewhat concave, the two extremities 

 thus remotely approach each other. The Infusorian when 

 in this condition often swims by rotation on the longitudinal 

 axis. 



Tachysoma parvistylum, sp. nov. (PI. III. fig. 8.) 



Body elongate-ovate, less than three times as long as broad, 

 widest posteriorly, narrowed anteriorly to form a neck-like 



