1921] NATURAL SCIENCES OF PHILADELPHIA. 163 



phores. They consist entirely of small fusiform bodies, regularly 

 disposed in two or three superimposed layers, with their long axes 

 in a line parallel to the surface of the body. They are very delicate, 

 and when compressed become rounded, showing at the same time 

 a central lighter region. All together, these fusiform corpuscles 

 make up a thick envelope, limiting a large clearer endoplasm, color- 

 less, half-liquid in appearance, which contains the nucleus. This 

 latter, very pale, consists of a homogeneous grayish plasma, with 

 here and there a few very small nucleoles. At the anterior end of 

 this colorless endoplasm, a large triangular space appears, the char- 

 acteristic reservoir, into which from time to time is seen to empty 

 the adjacent contractile vesicle; the reservoir itself communicates 

 with the outside by means of a narrow channel, which opens not 

 quite at the anterior extremity, but somewhat laterally. 



Of the two flagella, only one of them, the locomotor fiagellum, 

 can usually be detected. Both, however, have their origin in the 

 small depression where the channel of the reservoir opens, and, 

 so far as I could observe, start from the same spot, a little 

 within the opening and on the ventral side of the tube. Stokes 

 describes the locomotor fiagellum as "apparently originating in the 

 oval fossa; the other taking its origin on the ventral or lower sur- 

 face a short distance behind the anterior extremity, and usually 

 traihng, but I should not be surprised if there was a mistake in 

 this statement. Further on the American observer continues: 

 "The trailing fiagellum is ordinarily extremely difficult to see. 

 When the Infusorian is rendered uncomfortable and sluggish by 

 prolonged confinement beneath the cover, or partially poisoned by 

 iodine, then the vibratile fiagellum, which is usually held stiffly 

 in advance, the tip alone trembling, is flashed into sight as a rapidly 

 undulating spiral, and the trailing appendage is also momentarily 

 directed forward. . . . It is scarcely possible to believe that 

 Stein would have failed to notice so important an appendage." 

 My own observations entirely confirm Stokes's statements; but as 

 for a mistake by Stein, I regard it indeed as quite possible. The 

 traiUng fiagellum is so extraordinarily thin, and its refracting 

 properties are so much like that of water, that it is only detected 

 with the utmost difficulty. I studied Trentonia for many days 

 without noticing any second fiagellum, which, however, was there; 

 afterwards, I was able to see it on many occasions. Some of my 

 observations seem to prove that when the animalcule is at rest^ 

 the accessory fiagellum lies stretched behind, and adheres with its 

 tip to the substratum, keeping the body in place. 



