164 THE ORGANIZATION 



Paramecium is one of the most common of its class wher- 

 ever stagnant water or substances decaying in water exist. 

 As it is so readily obtained, and so easy to observe on account 

 of its size, and because it has afforded me the best opportunity 

 of becoming acquainted with the structure of Infusoria, I shall 

 take the liberty of describing its organization with considerable 

 detail. Its figure may be compared to an elongated oval, with 

 one end flattened out (H) broader than the other, and twisted 

 about one third way round, so that the flattened part resembles 

 a very long figure 8. The latter corresponds to the disc of the 

 Stentor, Epistylis, &c. ; and in accordance with this we find 

 the mouth (m) opening near its edge, at a point which is half- 

 way between the two ends of the body. I hardly need repeat 

 to you that the disc is in the front region of the animal. Taking 

 this now as a basis, it is not difficult to see the resemblance to 

 the disc-region of Stentor, (fig. 30, s,) and that the moderate ob- 

 liquity and twist of that of the latter are only extended to a much 

 greater degree in Paramecium without disguising or changing 



its character in the least. The posterior 

 (fig. 96, T) half of the body of Paramecium 

 then corresponds to the slender part of the 

 trumpet-shaped Stentor. A foreshortened 

 view of the anterior end (fig. 97) of the 

 " former bears a still more striking resem- 

 blance to the disc of Stentor. In both we 

 have the mouth (fig. 30 and fig. 97, m) at 

 the bottom of a broad notch or incurva- 

 tion, and the contractile vesicle (cv 1 ) on the 



opposite side, next the convex back, whilst the general cavity of 

 the body lies between these two. Confining myself now to Para- 

 side. H, the head ; T, the tail ; nz, the mouth ; m to g, the throat ; a, the pos- 

 terior opening of the digestive cavity ; cv 1 , the anterior, and cv, the posterior 

 contractile vesicles ; i, n, m, the radiating canals of cv 1 ; n, the reproductive 

 organ ; v, the large vibrating cilia at the edge of the vestibule. Original. 



Fig. 97. The same as fig. 96, seen endwise; i. e., foreshortened from the 

 head backwards. Letters as in fig. 96. Original. 



