328 M. A. Schneider's Contributions to the 



On close examination, one or two reddish lines may be seen run- 

 ning backwards from the bottom of the indentation (fig. 25), 

 which might readily be taken for organs lying in the interior of 

 the body. I have convinced myself, however, especially by the 

 comparison of the process of division in a species of Bodo, that 

 these lines indicate furrows, which gradually divide the whole by 

 cutting deeper and deeper on each side. As during this process 

 the animal undergoes no change of form, except in becoming a 

 little broader, and the division takes place along its whole 

 length, the process must readily escape observation. The ante- 

 rior end is always a little thicker ; the furrows consequently arc 

 deeper and more distinctly recognizable in that part. With a 

 suitable arrangement of the microscope, it is evident that, the 

 two furrows being looked at simultaneously, two reddish lines 

 are seen. It is only in rare cases, when the division has taken 

 place more slowly in some particular spot, that the two spe- 

 cimens must endeavour to tear themselves free, and thus, by 

 twisting in contrary directions, draw our attention to them. That 

 the process of division is effected in a similar manner in other 

 Monadina, appears from an observation of Ehrenberg's upon 

 Cryptomonas cylindrica (p. 42) : — " I saw no instance of constric- 

 tion or fissation, but two individuals were swimming whilst ad- 

 hering together, which might lead one to suppose that a longi- 

 tudinal division from behind forwards had taken place." And 

 it is not improbable that the specimen represented by him on 

 tab. ii. fig. xix. 2, with two seminal glands (nuclei ?) and two 

 longitudinal lines, was in the act of division. 



The occurrence of an encysted or quiescent state in Polytoma 

 cannot be considered remarkable, since Stein has made known 

 the encystation of Vorticella microstoma*, and Colin that of Tra- 

 chelitis Ovum, Trachelocerca Olor, Holophrya Ovum, Prorodon 

 teres and Chilodon uncinatus^. To this list I can add some others 

 from my own observations. Stylonychia pustulata, Ehrbg., gra- 

 dually acquires a spherical form, still retaining its cilia ; the cilia 

 then quickly fall off, continual little contractions take place, and 

 a clear mucus is secreted by the whole surface, which gradually 

 hardens into a strong, solid membrane. When a spherical spe- 

 cimen is obtained, the casting off of the cilia and the secretion of 

 the membrane may easily be followed under the microscope. 

 The exclusion of the animal completely furnished with cilia may 

 often be observed, merely by re-establishing fermentation in the 

 fluid. The animals which are somewhat elongated previously 

 twist round spirally with great rapidity within the cyst. 

 After exclusion, they present a remarkable resemblance to 



* Wiegmann's Archiv, 1848. 



f Sicbold nnd Kollikcr's Zeitsehrift. iv. 



