ORDERS OF THE IXFUSOR1A. 357 



1854 was owing to the presence of prodigious numbers of this species of Melodinium* (Fig. 4, A). The 

 tint was sometimes uniformly diffused through the water, and at others was collected in dense clouds, 

 vary ing- from a few to upwards of 100 square yards in extent. Later on, the coloration of the ponds, 

 brought about by the agency of these minute organisms, had much increased in density. By the 9th 

 of July the water was so dark and brown, that a white disc, half an inch in diameter, was invisible when 

 plunged to a depth of from three to six inches ; while a copious exit stream, constantly flowing away 

 from the ponds, presented a similar deep brown hue. In many places the animalcules had descended 

 from the surface, and were found congregated in immense masses near the bottom of the water. In these 

 instances they had, for the most part, become quiet ; the flagellum and cilia had disappeared, and a kind 

 of transparent tissue had been developed around each one. During the life of these curious animalcules 

 the body divides across, and two individuals are formed ; and this proceeds time after time, adding 

 rapidly to the numbers of individuals. Moreover, the encysted state is accompanied by a breaking- 

 up of the internal protoplasm or endoplasm into numberless particles, each of which will grow into a 

 form resembling the parent. 



In examining the phosphorescence of the sea, moderately large animalcules of -g^th of an inch 

 long are occasionally seen. They are light-emitting, of a yellow colour, and have a remarkable shape 

 and construction. An external coat, transparent but hard, exists, and it covers the soft structures. 

 It is prolonged into a long horn in front and behind, and the body is nearly globular, with a depression 

 around it, and a groove crossing this at right angles. The appearance is very peculiar. Cilia 

 bound the depression, and a very long and delicate flagellum, which moves like the lash of a whip, 

 starts from the groove. The long fore-and-aft projections are quite stiff, and the only mobile parts 

 are the cilia and flagellum. This Infusorian belongs to the same order as the last, and to the genus 

 Ceratiumt (Fig. 4, n). They are CILIO-FLAGELLATA. 



A very different kind of animalcule must be taken, as the example of the next and last order of 

 the Infusoria. If the surface of water-plants in the Birmingham and Stratford Canal, for instance, be 

 observed, a fine Infusorian -^th to y^th of an inch in length may be seen fixed on a long stalk which 

 is straight and stiff. The body, placed at the top, is contained in a cup-like sheath, with a triangular 

 outline, widest where free, and where there is a slit which enables the endoplasm 

 to communicate with the water outside. The endoplasm (finely granular) does not 

 fill the cup, but collects in an egg-shaped mass which has a contractile vesicle, and 

 the nucleus or endoplast is in the form of a band. There are neither cilia nor a 

 flagellum, but a bundle of numerous tentacles exists at both ends of the free end 

 of the cup-shaped sheath, and they are processes of the body. The tentacles have 

 a disc-like top, and do not move so as to enable the animal to swim. They are 

 catchers of prey, and any small animalcule coming in contact with them is stopped, 

 and its delicate tissue is penetrated by their sucker-like disc (Fig. 5) J. By-and-by 

 the endoplasm of the victim is sucked out of it, and acts as the food of the catcher. 

 The young of these stationary Infusorians are active, and move well and rapidly 

 with the aid of cilia, and thus resemble the Ciliate Infusoria. These Infusoria -p. . _ 

 constitute the order TENTACULIFERA. TUBEROSA, WITH 



There are, then, four great groups or orders of Infusoria typified by the TENTACLES EX- 



-n 'ft TJT i T i A 1 PANDED AND CON- 



species of the genus .raramecium, Cercomonas, Melodinium, and Acineta, and TRACTED. 

 they constitute the orders Ciliata, Flagellata, Cilio-flagellata, and Tentaculifera. 



A host of species, included in numerous genera, is classified under each of these orders, and there 

 is the greatest diversity of shape and of method of life amongst them ; but the main features and especial 

 characters of the orders are so definite, that there is no difficulty in classifying any Infusorian, which 

 has attained adult age, in its proper group. 



From their great vivacity of movement, their many varieties of cilia, the invariable existence of 

 contractile vesicles, and endoplasts, and sometimes trichocysts, the Ciliata, or the Infusoria which 

 move by and are more or less covered with cilia, strike the observer as of predominant zoological 

 importance. They are clearly more highly organised than the Infusoria which have only flagella. 

 And these last appear to be lower in the animal scale than the creatures which have a few cilia, 

 * Melon, a peach ; dine, a vortex. f Ceratium fusus. Acineta tuberosa (Ehrenberg). 



