OF THE PROTOZOA. ACTINOPHRYINA. 247 



alternate eontractions and expansions of the whole body. Other motions can 

 affect both the filaments and the body, but in any case only through the 

 slowest possible contractions." Besides these ill-understood translations 

 from place to place, and those movements chiefly affecting the tentacles in 

 the act of taking in food, to be presently noticed, there also occur, according 

 to Kolliker, ^' faint indications of contraction, such as slight undulations of 

 the border, and inconsiderable quivering motions here and there. The creature 

 also seems to be capable of altering its entire form to a certain extent, and to 

 be able to expand and to contract itself in toto^ Stein contradicts these 

 statements, affirming that he could neither observe any movement in the 

 organic mass, nor any change of position, whilst Claj)arede, on the other 

 hand, writes, '^ nevertheless the animal, in its ordinary sun-like form, is able 

 to move slowly in a given direction ; but during this movement no contraction 

 of the body or bending of the tentacles is to be observed." A singular obser- 

 vation is recorded by Mr. Boswell {T. M. S. 1854, p. 25), which needs con- 

 firmation before it can be accepted, viz. that the Actinophryina can suddenly 

 change their place by a leap. This phenomenon, he tells us, he witnessed 

 twice among a number of the animalcules found floating on the suiface of the 

 water. Usually the Actinophrys is found attached to some object, and that 

 so firmly that large animalcules may strike against it, or strong succussions 

 of the water take place without loosening it from its hold. Podoplwya and 

 Demh'osoma are exceptional Actinopliryina, by possessing a pedicle. In the 

 former this stem is commonly short and always simple, whilst in the latter 

 and hitherio little-known genus it is branched. As elsewhere noticed, Stein 

 will not admit the pedicle of Podophrya to be a generic, indeed not even a 

 specific, distinction, and therefore treats Actinophrys and Podophrya as 

 identical. In connexion with his belief in the presence of an enclosing 

 integument, he describes the wall of the hoUow pedicle of Podophrya to be 

 continuous upwards with the external envelope of the body (XXIII. 3, 4). 

 It is proper, however, to remember that Stein wanted both to establish his 

 hypothesis of the conversion of Vorticella into an Actinophrys and Podophrya, 

 as a consequence of the act of encysting, and preparatory to embryonic repro- 

 duction, and, further, to assimilate those genera with various Acinetce, which, 

 in his opinion, were derivable from other members of VortlceTlina. This 

 detracts from the value of his details of the structure and functions of Actino- 

 phrys ; and, as expressed above, a great doubt suggests itself whether he has 

 always examined the selfsame animalcules, and whether what he has de- 

 scribed applies to the Actinophrys investigated by Kolliker and Claparede. 

 Cienkowsky, who has latterly tested Stein's hypothesis, asserts, respecting 

 the question of the structure of the stem of Podophrya, that the pedicle is 

 an appendage to the body, which has no integument. " I am unable " (op. 

 cit. p. 100), he writes, " to adopt Stein's view that the Podophrya are enclosed 

 in a membrane, of which the slender pedicle is simply a tubular protrusion. 

 This is true only with respect to the short peduncle of the encysted Podophrya " 

 (XXIII. 36, 37). 



Prehension and Entrance of Food. — The movements of the tentacula of 

 Actinophryina are chiefly directed to the prehension of prey for food. This 

 they eff'ect primarily by seizing it by means of their apparently sticky surface, 

 and then, by shortening themselves, drag it to the surface of the animalcule. 

 If the prey has been caught by one tentacle, the neighbouring ones conspire to 

 clutch it more firmly, and (to use Kolliker's words) " apply themselves upon 

 it, bending their points together, so that the captive becomes gradually en- 

 closed on aU sides." This concui'rence and crossing of the tentacles is men- 

 tioned also by Stein ; but Mr. Weston states that he has never witnessed it. 



