150 M. E. Penard's Notes on some Ileliozoa. 



jyhrys. As to the rigid threads, they have been seen to 

 traverse the body of the animal and to converge towards a 

 common centre, where there was a central granule brightly 

 stained by carmine. 



In other respects the pseudopodia of the Acanthocystid.es 

 present the same phenomena as those of Actinophrys • they 

 are rigid or soft according to circumstances, and they reti'act 

 suddenly upon themselves during the passage of a stream of 

 water, forming globules like those of a thread of glass exposed 

 to a flame. 



It is by means of these long pseudopodia that the Heliozoa 

 move upon the mud or run over aquatic plants. TheActino- 

 phrydians, however, most frequently appear motionless ; but 

 sometimes, for example when a colony breaks up, the individuals 

 are animated by a perceptible movement ; we then see that they 

 pull upon their anterior pseudopodia, the points of which they 

 have stuck to the soil, while the posterior ones drag behind, 

 become elongated by traction, and finish by detaching them- 

 selves and shortening. The lateral pseudopodia, also fixed 

 to the soil by their points, likewise drag a little behind, so 

 that from the general appearance of the animal we can foresee 

 the point at which it will finally arrive. 



As to the Acanthocystides, the movements of which are 

 sometimes so rapid that they traverse in one minute a course 

 equal to ten or twelve times their diameter, I have succeeded 

 after a very careful examination in explaining them in the 

 following manner : — The animal, resting on its pseudopodia 

 like a cursorial spider upon its legs, throws out in front some 

 of these pseudopodia ; these attach themselves to the soil by 

 their points, which are at the moment viscous and perhaps 

 also slightly dilated into heads ; then, stiffening, they draw 

 the animal towards them ; the body, while advancing slightly, 

 turns a little upon itself from behind forwards, probably be- 

 cause the cords or pseudopodia which drag it originate above 

 the equator of the animal ; new pseudopodia, always antero- 

 superior, then attach themselves by their points in front of 

 the foimer ones and stiffen in their turn. This movement 

 continuing and the anterior cords pulling while the posterior 

 ones detach themselves one after the other, often with a small 

 sudden shock, and the lateral ones seeming to steady the whole, 

 the animal progresses by rolling continually over and over, so 

 that, by transmitted light, we see all the excentric elements, 

 prey or granules, contained within the body traverse this 

 body in a straight line, at first from behind forward and then 

 from in front backwards. It must be remarked that during 

 locomotion the body appears to turn much too slowly rela- 



