PROTOZOA: RHIZOPODA. 5 1 



• There are no traces of any organs of sense, or of a nervous 

 system, or, indeed, of any other organs in addition to those 

 already described. Locomotion is effected, with moderate 

 activity, but in an irregular manner, by means of the blunt, 

 finger-shaped processes of sarcode, or pseudopodia, which 

 can be protruded at will from any part of the body, and can 

 be again retracted within it. The pseudopodia also serve as 

 prehensile organs ; but they do not interlace and form a net- 

 work, nor do they exhibit any circulation of granules derived 

 from the endosarc, as in many others of the Rhizopoda. 



As regards the reproductive process in the Amceba, no dif- 

 ferentiated sexual organs have hitherto been discovered, and 

 the true sexual form of the process is therefore unknown. 

 Fresh individuals, however, may be produced in three ways : — 

 Firstly, by simple fission, the animal dividing into two parts, 

 each of which becomes an independent organism. Secondly, 

 by the detachment of a single pseudopodium, which becomes 

 developed into a fresh Amceba. Thirdly, by the production of 

 little spherical masses of sarcode which may be derived from 

 the nucleus by fission, or may be produced by a segmentation 

 of the endosarc, the animal having previously become torpid, 

 and the nucleus and contractile vesicle having- disappeared. 

 These little masses, however produced, develop themselves 

 when liberated into ordinary Amcebce. This last method of 

 reproduction is obviously very closely analogous to the pro- 

 duction of " pseudonavicellae " in an encysted Gregarina. 

 It has been doubted, apparently with considerable reason, 

 whether the so-called Amxbce are distinct species of animals, or 

 whether they are not rather transitory stages in the life-history 

 of other organisms. It is quite certain that several of the 

 Protozoa pass through an Amoeboid stage, and it is also certain 

 that vegetable matter not uncommonly assumes similar char- 

 acters {e.g., the mycelium of certain fungi). It is therefore 

 not impossible that the forms known to the microscopist as 

 AmoebiE may be ultimately discovered not to be permanent 

 and distinct species j but the evidence on this head is still 

 defective. 



The remaining members of the Amabea are constructed 

 more or less closely after the type of the Amaba itself In the 

 nearly allied Difflugia, the sarcode forming the body of the 

 animal is invested with a membranous envelope or " carapace,' 

 strengthened by grains of sand and other adventitious solid 

 particles, and having a single aperture at one extremity, 

 through which the pseudopodia are protruded (fig. 2, b)'. The 

 animal generally creeps about head-downwards, so to speak ; 

 4 



