252 



The Field Naturalist 's Quarterly 



August 



Exactly the same processes, minus the self-division, are gone through, 

 when for any reason a Vorticella wishes to shift its quarters. In such 

 a case it withdraws the ciliary wreath, forms another at its attached 

 end, breaks away from its stem, attaches itself anew by its ciliated end, 

 withdraws those cilia, grows a stem, and opens another ciliary wreath 

 at the opposite end. 



Like Amceba, Vorticella encloses itself in a cyst to pass the period 

 of rest between one season and another. It may become encysted 

 either on its stem, or when detached. 



It will be seen then that although Vorticella is more specialised than 

 Amoeba, since it has particular parts appropriated as organs of nutrition 

 and locomotion, yet it is still a very simple unicellular organism, both 

 the mouth and oesophagus, cilia and stem, being mere appendages and 

 prolongations of the cell-wall and protoplasm. 



The veteran microscopist, Ehrenberg, called these Infusoria " Poly- 

 gastrica " ( = many-stomached animals), under the impression that the 

 food vacuoles in the body were a series of stomachs connected by an 

 intestine. The fact that Vorticella has a mouth and gullet leant colour 

 to this belief, but its fallacy is evident from the fact that the entire 

 contents of the body are constantly, though very slowly, revolving within 

 the cell-wall. This I discovered by keeping a single individual under 

 examination, with a J-inch objective, for a considerable time, and 

 noting the changes in position of the more solid particles in the 

 protoplasm. 



A boy who saw a giraffe for the first time remarked that it must be 

 nice to have a long neck like that, because one could taste things for 

 m<M^ such a long time in swallowing ! The giraffe 

 amongst Infusorians is Ophrydium (Fig. n), 

 which is practically a Vorticella with a very 

 small head but a very long neck and body. 

 The length of its "swallow" becomes very 

 apparent if it be fed with carmine or Prussian 

 blue. The commonest species of Ophrydium 

 (O. versatile) is of a bright green colour. It 

 occurs in pools and canals in the form of pale 

 green gelatinous balls about the size of a walnut, 

 or larger. The species is interesting as being 

 an example of the most primitive form of 

 colony. The gelatinous matter is the joint 

 product of all the individuals, and unites them 

 into one mass. Each is embedded in it except 

 the head with its ciliary wreath, which, when 

 fully expanded, projects beyond the periphery. 

 Each can withdraw itself within the mass at 

 will, or, if so disposed, can quit entirely, swim 

 away, and settle down elsewhere, secrete a new gelatinous sheath, and 

 by continuous division produce a new colony. 



Certain members of the genus Epistylis (Fig. 12, distinguished from 



Fig. II. — Ophrydium. 



a, Colony. 



b, Portion of same. 



c, Individual. 



d, Nucleus. 



