362 NATURAL HISTORY. 



most Infusoria, and the smallest animalcules or monads belonging to the Flagellata have a pale 

 glaucous or fluorescent hue, and Saville Kent notices that this is visible under high magnifying 

 powers. It is probably due to reflected and not to transmitted light. Most of the Flagellata are 

 coloured, and the species of one great group, the Euglenidse, are of a brilliant green, the colour 

 being diffused in the endoplasm. The colour is identical with that of the lower plants, containing 

 chlorophyll, and it is remarkable that this green tint should turn to red. Thus in Astasia sanguined, 

 the green colour, which gives a tint to the water in which the myriads of the animalcules swim, is 

 suddenly turned to red, accounting for old and new traditions regarding the turning of fresh waters 

 into blood. Ray Lankester has shown that in the genus Stentor the green matter, like that of 

 Hydra viridis and Spongilla, is a chlorophylloid substance similar to that of plants. One Stentor, 

 however, has a blue colouring matter which is produced by a special chemical combination called 

 Stentorin. Quite as many Infusoria have a diffused pale amber to deep olive colour as green, and 

 most of the Tentaculifera and Cilio-flagellata have these dull colours. 



Saville Kent notices that some of the Flagellata differ from the majority by the presence of 

 the olive colouring on two lateral bands on the body. In the Ciliata, a Leucophrys is of a 

 brilliant crimson colour, and a Nassula has numerous violet granules in its endoplasm. Minute 

 crimson granules have also been noticed in the contractile tissue of the stalk of Vorticella. 



In some Euglenidse, there are bodies in the green endoplasm which are of a starchy nature. 

 Finally, there are the accessory structures of the cortical part of some of the Infusoria or the 

 trichocysts. As has been already noticed (p. 355), they are visible in Paramecium aiirelia, in 

 the form of very slender rods crowded together in a layer, their points looking outwards beneath 

 the outer cuticle. Under the action of weak acetic acid, these trichocysts force through the 

 cuticle and beyond the cilia. Ellis, an Englishman, writing more than a century since, discovered 

 these curious bodies ; and Allman, in 1855, established their true nature, and assimilated it to a 

 certain extent with that of the nematocysts of the Corals. But there are essential distinctions. 

 Allman found that the minute fusiform rods, under external irritation, become suddenly transformed 

 into long hair-like filaments, which projected from the whole surface. By carefully crushing 

 examples, and isolating the trichocysts in their unaltered condition and in their fusiform shape (that 

 is, swollen in the middle, and narrow at each end), it was found that after a few seconds the shape 

 was altered with a jerk, as if some previous state of tension were relieved. A spheroidal shape was 

 assumed by the hitherto fusiform rod. Then, in a few seconds, a spiral filament was observed to 

 become rapidly evolved from the sphere, apparently through the rupture of a previously confining 

 membrane. The spiral fibre unwound, and became straight and rigid. In their most extended state, 

 these bodies were found to consist of a long rigid spiculum-like half, shai-p at one end, and continued 

 at the other into a very filiform part, which is bent more or less. 

 Probably they have a noxious influence on minute living things. 



Some Infusoria appear to retain the same shape under all kinds of 

 circumstances ; others enlarge laterally or longitudinally, and even twist,, 

 as they move here and there or endeavour to get in between substances, 

 but they speedily return to their normal figure. Such irregular changes of 

 shape as are seen in the Amoeboid s are not often found in the Infusoria, 

 but a very different appearance is presented by some during active motion 

 and feeding and during quiescence. 



(Aflefs^Kmt* Nothing is more common than to see many Ciliated Infusoria moving 



A, Bbowing^oniameBtMioii ; u, along with the shape of their bodies altered by the presence of a greater 



or less central constriction, and if one of them is watched, it will be seen 



to separate, into a front and a hinder part, and each will become a separate individual 

 (Fig. 13). Division also occurs length wise. It has been computed that, in the instance of 

 Stylonychia mytilus (p. 371), no less than a million of independent beings were derived 

 from repeated fission of a single individual in the course of ten days. When Infusoria form 

 colonies, they arise from the repeated binary subdivision of the first stock, and in some instances 

 masses result, slime-like, many feet in extent (Epistylis yrandis, p. 370). In the majority of species, 

 the division is across the body, and in others in a longitudinal direction, especially in the 



