1903 



British Field Zoology 



2 53 



Vorticella by not having a spiral muscle in the stem) attach themselves 



to the bodies of Water-Fleas, and thus, with no trouble or exertion to 



themselves, get carried far and wide. They are 



not parasites, since they draw no nourishment 



from the animal which bears them, though they 



probably pick up a good many " crumbs " from 



its meals. 



In another genus, Vaginicola (Fig. 13), two 

 individuals (each closely resembling an Ophry- 

 diuni) dwell together at the bottom of a grace- 

 fully proportioned clear vase attached at its 

 base to the water-weed. There seems a good 

 understanding between the two little hermits, for 

 they rarely both expand their ciliary wreath at the same time, and if they 

 do, one pushes it out farther than the other, so as not to incommode its 

 companion. 



So far we have noticed cilia as the chief source of 

 motion amongst the Infusoria. In many forms, how- 

 ever, instead of a number of short vibrating lashes, the 

 animal is provided with a single very long whip-lash 

 called a flagcllum. (Some forms have two flagella.) 

 These flagella work either by a rippling movement 

 travelling rapidly along from base to tip, or a slow 

 whip-like movement — the lash alternately bending and 

 straightening. In the case of free organisms both 

 these movements propel the animal forward, but I have 

 seen certain species travelling along with the flagellum 

 in frotit — a most mysterious proceeding. Euglcnaviridis (Fig. 14) is 

 a familiar example of a flagellate Infusorian. It occurs in stagnant 

 pools in farm-yards, and its 

 countless millions colour \ 



Fig. 12. — Epistylis. 



Two colonies attached to 



Cyclops. 



-*M& 



-b 



^-r--A 



Fig. 13.— Vagi- 



iiic ola. 



Fig. 14. — Euglena viridis. 



a, Nucleus. 



b, Contractile vesicle. 



c, Eye-spot. 



the water a bright opaque 

 green. 



The Infusoria present 

 such an endless variety of 

 strange and beautiful forms 

 that only a very few can be 

 mentioned in a paper such as this, which aims rather at giving a general 

 idea of structure and function than zoological characters. Anyone wish- 

 ing to study the group further, or to identify genera or species, will refcr 

 to Mr. Saville Kent's Manual of the Infusoria. 



We will conclude by taking two examples showing interesting modi- 

 fications of structure — Paramecium and Stylonychia. 



Paramecium (the Slipper-Animalcule, Fig. 15) is easily obtained in 

 water in which hay or other vegetable matter has been steeped for a 

 week or two. It is covered all over with powerful cilia, and is extremely 

 active in its movements, darting hither and thither in the most erratic 

 manner. Watching it under a i-inch objective, the observer will notice 



