322 M. A. Schneider's Contributions to the 



As it appeared desirable that we should be better acquainted 

 with the mode of division of Polytoma, I have made a series of 

 observations upon this elegant creature, the results of which will 

 be found in the following pages. The material for the investi- 

 gation is easily obtained. Polytoma Uvella is to be met with in 

 every puddle, in rain-water tanks, &c, and its rapid increase 

 may readily be effected, by the putrefaction of animal or vege- 

 table matters. 



Polytoma Uvella is of an oval form ; it is from ^o to ^ of 

 an inch long, and about half that width. At one end, which, 

 with Ehrenberg, we will call the anterior extremity, it bears two 

 filaments as long or longer than the body. When the living- 

 animal is examined under a magnifying power of 300 diameters, 

 the body appears to be bounded by a simple outline. But in 

 many instances, and especially when a large specimen can be 

 found at rest, it may be seen that the internal substance of the 

 body is surrounded by a thin and perfectly clear membrane, 

 from which it is separated by a distinct space. When the in- 

 vesting membrane is more closely attached, its existence may 

 always be demonstrated by the employment of reagents to pro- 

 duce the contraction of the substance of the body : chromic acid 

 and solution of iodine in chloride of zinc are the best substances 

 to employ, the latter especially, as it at the same time communicates 

 a brown colour to the internal sac (PI. XI. fig. 2). Under cer- 

 tain circumstances, the investing membrane divides into minute 

 granules, assuming when viewed from the side a regular neck- 

 lace-like appearance (fig. 8). A reproduction of the membrane 

 then takes place. The substance of the body is perfectly clear, 

 with the same refractive properties as that of Amoeba. About 

 the middle lies a clear, globular nucleus, surrounded by a nar- 

 row, reddish halo. Dilute acids render this more distinct. At 

 the anterior extremity, close to the margin, there are two reddish 

 vesicles, the contractions of which may easily be recognised in 

 individuals in a state of repose. The hinder extremity always 

 contains a mass of granules, with dark outlines, which are not 

 altered by acetic acid. A weak solution of iodine in iodide of 

 potassium gives them a deep blue colour, generally verging upon 

 black, as it is difficult to hit the right quantity of the reagent to 

 be added. The fine blue colour is better attained by the addi- 

 tion of diluted solution of iodine in chloride of zinc, as with this 

 the granules become slightly liquefied, and when left standing 

 for some time even form a blue paste. Muriatic and sulphuric 

 acids also dissolve them, so that the subsequent addition of 

 iodine gives the whole body a blue colour. When the putrefac- 

 tion of the infusion is going on very rapidly, the granules fill the 

 entire body. They are not arranged in balls like the nutritive 



