408 MICROSCOPIC FORMS OP ANIMAL LIFE. 



of the latter is generally flattened, yet it sometimes becomes nearly 

 spherical; so that neither type can be recognized, until the jelly- 

 like spherule flattens itself out as an Amoeba, or pnts forth radi- 

 ating "pseudopodia" as an Actinophrys. Far less activity is ex- 

 hibited by Actinophrys, than by Amceba ; and the slight change 

 of place which it undergoes from time to time, does not seem at- 

 tributable either to any change of form of the body, or to anj- 

 bending of the tentacles. It is by the agency of these, however, 

 that its nourishment is obtained ; and this is derived not merely 

 fk-om vegetable particles, but from various small animals, some 

 of them (as the young of Crustaceans) possessing great activity, 

 as well as a comparatively high organization. When any of these 

 happens to come into contact with one of the tentacular fila- 

 ments, this usually retains it by adhesion, and forthwith begins 

 to retract itself ; as it shortens, the surrounding filaments also 

 apply themselves to the captive particle, bending their points 

 together so as gradually to enclose it, and themselves retracting, 

 until the prey is brought close to the surface of the body. The 

 threads of " sai'code" of which the "pseudopodia" are com- 

 posed, not being invested (any more than the sarcode of the 

 body) by any limiting membrane, coalesce with each other and 

 with it ; and thus the particle which has been entrapped by them 

 becomes actually embedded in the gelatinous mass, and gradually 

 passes from the peripheral towards the central part of it, where 

 its digestible portion undergoes solution, the superficial part of 

 the body, with its pseudopodial prolongations, in the meantime 

 recovering their previous condition. Any indigestible portion, 

 as the shell of a Crustacean, or the hard case of a Rotifer, finds 

 its way to the surface of the body ; and is extruded from it by 

 a process exactly the converse of that by which it is drawn in 

 (Fig. 192, d). The number as well as the size of the particles 

 included by the Aotinoplirys at any one time is very various ; 

 frequently they are more than ten or twelve. They are not 

 usually embraced closely by the sarcode, but are surrounded by 

 fluid in "vacuoles" in its substance; and it was this appearance 

 which led Prof. Ehrenberg to describe the animalcule as possess- 

 ing numerous stomachs. The Actmojyhri/s, like the Amoeba, 

 multiplies itself by self-division ; but a process which seems to 

 resemble the " conjugation" of Protophytes (§ 151), has also 

 been witnessed in it by Prof. Kolliker and Dr. Cohn.' Two in- 

 dividuals approximate and coalesce, so as to form what appears 

 to be a single body; but a " nucleus" then makes its appearance, 

 which gradually developes itself into a mass having the charac- 

 ters of its parent; and the young Actinophrys thus generated 

 probably escapes, before long from the body within which it 



' It appears probable, from the recent observations of Mr. Weston (Quarterly Journal 

 of Microso. Science, Jan 1850), and olliers, that the supposed " conjugation" of Acti- 

 nophrys is a mere fusion of two bodies wliicli may separate again unchanged, and is 

 not a generative phenomenon. Tlje same would appear to be true of it in this respect, 

 as of Gregarina (§ 30bj. 



