450 Dr. G. C. Wallich on the Distinctive Characters, Habits, 



The pseudopodia, however, soon begin to extend, and finally 

 cover the greater portion of the surface. As they increase in 

 number, the power of locomotion and projection of the ordinary 

 pseudopodia ceases ; and ultimately the structure seems to un- 

 dergo a period of nearly complete quiescence, during which the 

 pseudocyclosis does not continue, and the alternating action of 

 the contractile vesicle is very slowly carried on without removal 

 from the villous region. (See Plate VIII. fig. 11.) 



Lastly, after varying periods, these Actinophryan pseudopodia 

 are, one by one, retracted into the substance of the body ; loco- 

 motion recommences in the usual manner, and with it the pseudo- 

 cyclosis; and we have again presented to us the entire cha- 

 racteristics of Amoeba villosa. 



Whether the transition between Amoeba and Actinophrys is 

 ever of a permanent nature there are no means of determining 

 in the present state of our knowledge. But, although unable 

 to perceive any valid ground for doubting its possibility, I would 

 observe that the line of demarcation between the two genera is 

 sufficiently marked to render it available for purposes of classi- 

 fication. In short, whilst the shape, dimension, and number of 

 the pseudopodial processes appears to be determined, in a great 

 measure, by accidental and varying conditions of the medium by 

 which they are surrounded, their physiological characters remain 

 nearly unaltered. 



The prehensile faculty in Amoeba and Actinophrys is very dif- 

 ferently brought about in the two genera. In Actinojjhrys it is 

 similar in kind, but far superior in extent, to that present in the 

 Foraminifera and Polycystina, and is principally dependent on 

 the adhesive viscidity of the ectosarc. In Amoeba, the ectosarc 

 possesses little or no adhesive power, except in the villous region, 

 and an object is held or dragged towards the body simply by 

 being encircled and then subject to the contractile action of the 

 sarcode. Hence it is evident that the ectosarc of the villous 

 appendage of Amoeba, in which a powerful prehensile power 

 resides, is not differentiated to the same degree as that of the 

 rest of the surface. This fact, which analogy would lead us to 

 expect (since it is only at the villous region that the contractile 

 vesicle discharges itself, and effete matters are extruded), is 

 strengthened by the near approach in character of the villi them- 

 selves to the ciliary legs of Ploesconia and Kerona, inasmuch as 

 the latter organs are the only portions of these creatures in which 

 the tendency to sudden solution of continuity is observable. 



It is deserving of special notice, moreover, that the facility 

 with which coalescence takes place between the pseudopodia, and 

 the adhesive faculty of the ectosarc, are such mutually dependent 

 conditions as to be inseparable. In Lieberkuhnia, the Forami- 



