• Fresh-water Rhizopod. 257 



ingested water must be supposed to be got rid of by passing 

 into the vessels in connection with the contractile vesicle, and 

 by being thus expelled from the body. 



For an account of the anatomy of the Protozoa, see KoUiker's Icones 

 Histiologicae, Abtheil. i., pp. 9-24, 1864; Stein, Organismus 

 der Infusionsthiere, Abtheil. ii., pp. 1-140, 1867; Claparede et 

 Lachmann, Etudes sur les Infusoires et les Rhizopodes, vols. i. 

 and ii., 1858-1861 ; Extr. des tomes v. et vii. I'lnstitut 

 Genevois; Leuckart, Die Menschlichen Parasiten, p. 135. 



For an account of the genus Prorodon, see Claparede et Lachmann, 

 I. c, vol. i., 318. 



FiGUEE 9. 



Amoeba RacUosa, a fresh-water Rhizopod ; aff.er Auerbach, Zeitschrift fiir Wiss. 

 Zoologie, viii., Taf. xxi. 



Showing its pseudopodia, its contractile vacuoles, its nueleolated 

 nucleus, and the algae and navicellae which it has enveloped in the 

 substance of its parenchyma. The central portion of the body is 

 very ordinarily of about the size of a human white blood-cell, and 

 the pseudopodial processes may be as long as from twice the length 

 of the diameter of the central mass up to as much as five times as 

 long ; but the size and shape both of body and of pseudopodia are 

 very variable, and make the distinction of species a matter of 

 much uncertainty. 



a. One of the pseudopodia. The pseudopodia differ from those 



of most other Rhizopoda in not being branched at their 

 apices ; in not anastomosing with each other ; and, as this 

 figure shows, in not having the granular substance of the 

 central parenchyma body circulating within them. Tlie 

 * sarcodic expansions,' as the pseudopodia have been called, 

 are very usually more broadly lobate than those figured 

 here ; it is by their alternate protrusion and retraction, from 

 which these animals take their names, that locomotion is 

 effected. 



b. Nucleus and nucleolus. 



c. Contractile vacuole. The possession of vacuoles, as also of the 



s 



