THE AMERICAN MONTHLY 



[Janiiaiy, 



contract themselves into the gela- 

 tinous mass ; for when extended 

 they j)roject beyond the circumfer- 

 ence of the mass ; nevertheless, 

 there is much concert of action in 

 extending and contracting. The in- 

 dividual animal, in its natural con- 

 dition, is elongated in form, more 

 slender in proportion to its diame- 

 ter, and not so robust as 0. versa- 

 tile ; the body attains its greatest 

 diameter a short distance above its 

 point of attachment to the stem. 

 Commencing at that point, it gra- 

 dually increases until the extreme 

 diameter is attained, it decreases 

 for a short distance and then main- 

 tains a uniform size very nearly to 

 the mouth, where it enlarges very 

 slightly to the peristome, thus exhi- 

 biting, in a certain degree, the cha- 

 racteristic funnel-shape. The stem 

 is long and non-contractile, and ap- 

 pears to be attached near the center 

 and base of the jelly-mass ; in all 

 cases thus far observed, the single 

 stalk divides into two, and to each 

 branch an animal is attached. The 

 two animals thus united usually con- 

 tract together. These stalks are not 

 readily seen unless the mass is dis- 

 sected, or broken up by means of 

 needles and slight pressure on the 

 cover-glass. Sometimes the division 

 of the stalk appears near the point 

 where the animals are attached, at 

 other times it is more distant. I 

 have never seen the animals under- 

 going the process of iission ; that 

 they do undergo this longitudinal 

 division is, however, doubtless a 

 fact ; but the question naturally 

 arises, does the stalk also undergo 

 fission ? 



In no case is any axis visible in 

 the stalk with the powers I have 

 employed. I have often noticed 

 the stalks remaining in the jelly- 

 mass, after the animals have been 

 set free ; they then exhibit a slight 

 enlargement at the extremity, where 



the animal was attached. These 

 infusoria have been observed re- 

 posing with the peristome everted 

 and cilia extended. 



The peristome is annular, and 

 the disc projects some distance 

 above it, one side being a little more 

 elevated than the other, so that 

 most frequently, the peristome and 

 disc give the animal the appear- 

 ance, when viewed obliquely, of 

 possessing a triangular-shaped head 

 (so-called); with a one-inch ob- 

 jective this appearance is quite 

 characteristic ; the cilia act spas- 

 modically, some of the time they 

 are at rest. 



Although the cilia of the peris- 

 tome and disc generally act simul- 

 taneously, those of the one part 

 may act or rej)Ose independently of 

 those of the other part. 



In most cases the upper part of 

 the body bends slightly to one side, 

 thus representing the peristome 

 and disc inclined. 



The oesophagus is distinctly seen 

 opening on the disc ; it extends to 

 a point about midway between the 

 mouth and the contractile vesicle, 

 diminishing in size as it proceeds 

 downward ; it is provided with 

 three or four cilia which may be 

 active when those of the peristome 

 and disc are at rest, during inver- 

 sion or eversion. 



Near the lower extremity of the 

 oesophagus is a fusiform body, the 

 walls of which are resistant or non- 

 dilatable. 



The endoplast is a long cord-like 

 differentiation of the cortical sub- 

 stance, extending from above the 

 contractile vesicle down through 

 the body to the lowest part of the 

 dilated portion, almost to its point 

 of attachment with the stalk; it 

 makes several curves, and in some 

 places appears twisted ; it is not 

 readily seen except when the ani- 

 mal is either subjected to pressure. 



