M. E. Penard's Notes on some Heliozoa. lot 



tively to the distance travelled — that is to say that, instead of 

 traversing a space equal to about three times its diameter in a 

 complete turn, it is not until after executing- a much longer 

 passage that a complete revolution has been made ; this is 

 because the sphere which may be imagined as circumscribing 

 the animal is not represented by the body itself, but rather 

 by the extremities of the pseudopodia. 



Such, according to my observations, is the process of loco- 

 motion in the Heliozoa ; and this explanation would confirm 

 the opinion of Hertwig and Lesser, who, in a memoir, of 

 which, however, I had no knowledge until long after arriving 

 at my own conclusions, have described a Heliozoon as " rolling 

 after the fashion of a ball and by the contraction of the 

 pseudopodia." 



The pseudopodia of the Heliozoa, besides their functions as 

 locomotive organs, also play a certain part in the capture of 

 prey. In Actinojjkrys the little organisms which have fallen 

 among the pseudopodia as into a spider's web glide along 

 these threads until they arrive quite close to the body, at the 

 same time that a portion of plasma issuing from the ectosarc 

 advances to meet them, encloses them, and keeps them for 

 whole hours in a large vacuole full of liquid, in which they 

 are digested. The pseudopodia themselves may be active in 

 so far that they bend round the captured prey and draw it on ; 

 but this fact, although certain, is much more rare than is 

 generally supposed. 



In the Acanthocystides the phenomenon of the capture of 

 prey is still more interesting, and is at present known only in 

 its broad features. After having studied it in half a dozen 

 species I can describe it as follows, again taking Acautho- 

 cyslis turfacea as an example. 



When a small organism, such as a Monad for example, 

 comes in its course in contact with an Acanthocystis, the 

 radial spicules of the latter separate and lie down, at the same 

 time that a depression is formed at the spot upon which the 

 prey has fallen ; the bases of the spicules then change then- 

 position, moving in the very body of the mucilaginous layer 

 which bears them, and gain the margins of the depression, 

 where the spicules are soon seen accumulated in disorder; the 

 tangential scales do the same, and the whole mucilaginous 

 mass separates, thus leaving an opening in which the prey 

 finally comes into direct contact with the interior body or so- 

 called ectosarc of the Acantlwcystis. At this moment the 

 withdrawn mucilage begins to show an active movement all 

 round the Monad, and finally englobes it completely ; the 

 spicules ascend on their part, and tin 1 tangential scales, com- 



