72 MANUAL OF ZOOLOGY. 



or not, there can be little doubt but that the vesicles are a rudi- 

 mentary form of vascular apparatus. Others, however, hold, 

 with some probability, that the contractile vesicles are to be 

 regarded as excretory in function, and that they correspond 

 more with the water-vascular system of the Annuloida than 

 with the true blood-vascular system of higher animals. Certain 

 other spaces termed " vacuoles " are generally visible in addi- 

 tion to the contractile vesicles. These, however, are probably 

 merely collections of water surrounding the particles of ingested 

 food, and performing with them a circulation in the abdominal 

 cavity, something like the circulation of granules which is seen 

 in certain vegetable cells. It was the appearance of these 

 " vacuoles " — which are certainly not permanent organs of any 

 kind — which induced Ehrenberg to term ihe Infusoria the "Poly- 

 gastrica," upon the belief that they were so many stomachs. 



Paramxcium obtains its food by means of the currents of 

 water which are set up by the constantly-vibrating cilia. The 

 nutritive particles thus brought to the mouth pass into the 

 central abdominal cavity, along with the contents of which 

 they undergo the circulation above spoken of. Indigestible 

 and fsecal particles appear to be expelled by a distinct anal 

 aperture, which is situated near the mouth. 



Reproduction in Paramoscium is effected either non-sexually 

 by fission {i.e., by a simple division of its substance), or by a 

 true sexual process. In this latter method two Paramxcia 

 come together, and adhere closely to one another by their ven- 

 tral surfaces. The "nucleus," which is truly an ovary, enlarges, 

 and a number of ovules are formed in its interior. In like 

 manner, the " nucleolus " of each, which is really a testis or sper 

 marium, also enlarges, and develops in its interior a number 

 of fusiform or rod-like bodies, which are believed to be sperma- 

 tozoa. The liucleolus of each then passes into the body of 

 the other, the act of transference being effected through the 

 mouth. Contact of the two reproductive elements then, takes 

 place, and a number of germs are produced, which, after their 

 liberation from the body of the parent, are developed into adult 

 Parammcia. 



Vorticella (fig. ii, c) is a beautiful flower-like Infusorian 

 which is commonly found in fresh water, adhering to the 

 stems of aquatic plants. It consists of a bell-shaped body or 

 " calyx," supported upon the extremity of a slender contractile 

 stem or i' pedicle." The other extremity of the pedicle is 

 fixed to some foreign body, and its power of contraction is due 

 to the presence in its interior of a spiral contractile fibre, 

 which is sometimes called the "stem-muscle." The edge of 



