174 



HARDWICKE'S SCIENCE-GOSSIP. 



S. niger is a black species, and smaller than either 

 of the preceding. 



Unattached, Stentor is ovoidal in form. The 

 upper portion, which bears the peristome and closed 

 disc, is broader than the opposite extremity, which 

 ends in a hyaline sucker, by means of which the 

 organism fixes itself to a weed. When Stentor has 

 thus anchored itself it expands, the posterior end 

 lengthening, the anterior broadening, and the peri- 

 stome opening out, so that it assumes a form which 

 has aptly been compared to a trumpet, and gained 

 for it the name of the trumpet animalcule. 



The ectosarc is furnished with short cilia, which 

 cover the whole surface, a small tuft springing from 

 the tail. At the upper expanded portion there is a 

 circle of strong cilia springing from the peristome and 

 ending at the mouth in a spiral. 



The myophan striation, readily visible under a low 

 power, is yet more clearly analysed under a higher 



Wu- 1 



Fig. no. — Stentor Mtilleri. I, free swimming; 2, Stentor 

 expanded ; f, foot ; cv, contractile vesicle ; m, mouth. Low 

 power (1 inch). 



(Fig. 109, D). We can then study its nature, and 

 see that it does not merely consist of grooves, but 

 bands of less hyaline alternating with more hyaline 

 protoplasm. A grouping together of the more con- 

 tractile elements, we may say. 



A large contractile space is situated near the 

 peristome, and as in other Infusoria there are here 

 digestive vacuoles and granules, large and small, 

 scattered through the endosarc. Fig. 109, E shows 

 how, by squeezing one of these organisms between slide 

 and cover-glass, an appearance highly suggestive of 

 the network arrangement of the protoplasm, was 

 brought into view. The spaces between the meshes 

 seem to have been widened out. 



The chlorophyll corpuscles of 5. viridis resemble 

 those of Euplotes and the other Ciliata; some are 

 figured. The nucleus is composed of several separate 

 segments placed in a line like a row of beads, and 

 each component resembles an ordinary endoplast 

 (Fig. 109, c, «). 



Stentor is, I believe, sometimes classed apart from 

 the Vorticellinae. 



30. Vortkella nehllifera (Fig. m) might be well 

 chosen as an example of the whole group. A more 

 detailed description of several interesting particulars, 

 will shorten and facilitate the description of the 

 remaining species. 



The bell animalcule consists of an essential portion 

 or bell attached to a long stalk, whose other extremity 

 is fixed to some weed, very often to the stalks of the 

 duckweed. The bell is surrounded at the summit 

 by a wreath of strong cilia. These cilia are placed 

 on a ridge running completely round, and called the 

 peristome (Fig. Ill, /) ; inside this there is a disc 

 (Fig. in, d) also fringed with cilia. At a certain 

 point between the disc and peristome there is the 

 mouth, and it is above this orifice that the disc rises 

 highest when the bell expands. 



If we look down on to the expanded bell, we see a 

 groove between the disc and peristome which leads 

 to the mouth, and is known as the vestibule. 



The ectosarc is not very thick or dense, for the 

 outer surface is seen to slightly alter in form. 

 Sometimes one may see a transverse barring or 

 wrinkling similar to the myophan striation before 

 mentioned. A filmy or exudation layer is occasion- 

 ally observed secreted by the ectosarc. This 

 phenomenon is, I believe, known as " ecdysis." In 

 the specimens in which I observed this feature, the 

 exudation layer was transversely wrinkled and brown 

 in colour. A trace of the myophan striae is nearly 

 always observed where the bell joins the stalk 

 (Fig. Ill, my). The endosarc is faintly granular, but 

 sometimes filled with large, strongly refractile bodies 

 (Fig. III. g), which have been called spores, but 

 probably they have nothing to do with reproduc- 

 tion. The nucleus may be easily observed by 

 staining, or by the use of dilute acetic acid ; it is a 

 bent rod like a horse-shoe or letter S. In many 

 individuals it is evident without the use of re- 

 agents. The stalk consists of a delicate cuticular 

 sheath, through which runs a slender filament of 

 protoplasm. 



Having thus studied the general morphology of 

 Vorticella, we will consider the various movements 

 that take place in the different parts of its structure. 

 We may conveniently divide these into — 



1. Ciliary movements. 



2. Movements that result in the opening and 

 closing of the bell. 



3. Movements by which the bell is drawn down. 



4. Movements that take place in the internal 

 protoplasm. 



I. The cilia produce a very powerful current, 

 which draws food into the mouth and also whirls 

 digested particles away that have escaped from the 

 anal area. Elsewhere we had occasion to study the 

 general principles of ciliary motion, and it is un- 

 necessary to enter into them again. 



