M. E. Claparedc on Actinophrys Sol. 217 



dergoes an exactly similar change, under the same circum- 

 stances. 



The mode of feeding of Amceha and that of Actinophrys arc 

 evidently two allied plucnomena. This analogy has hitherto 

 escaped notice, except by Kolliker, princijjally on account of the 

 determinate form of Actinophrys, which contrasts strongly with 

 the extremely changeable and almost formless Amwbfc. I have, 

 however, frecpiently convinced myself that Actinophrys partakes 

 of this wonderful alterability of form. They may be found with 

 very long and very short tentacles, and these organs may even 

 entirely disappear. They may acquire every possible variety of 

 form (figs. 5 & G), but these changes take place far more slowly 

 than in Amaba, and the modification figured by Ehrenberg in 

 hx^i great work appears to be the typical form. 



Even the changeable Amoeboi have their typical forms, — such 

 as the stellate [A. radiosa, Ehr.) and globular. It is often diffi- 

 cult to determine whether we have to do with a globular Amoeba, 

 or with an Actino})hrys that has contracted its tentacles. The 

 most certain character in this case is furnished by the contractile 

 vesicle, which in Amoeba lies deep in the body, but in Actin- 

 ophrys (luite on the surface. Further observations soon settle 

 the question, as the doubtful animal will either extend the usual 

 thin processes of Actitiophrys, or convert itself into an unmis- 

 takeable Amoeba by expanding its body, which I have never 

 observed in Actinophrys. Actinophrys Sol is a very inactive 

 creature, and I have never been able to ascertain how its move- 

 ments are effected ; nay, for some time I was even doubtful 

 whether it was capable of any other movement than an ex- 

 tremely slow change of form, and the extrusion of the mucous 

 substance. 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. I must therefore leave the nature of the 

 movement undetermined, but the Actinophrys is far less active 

 than its near allies the Amoebce. Stein indeed thinks that the 

 locomotion of Actinophrys is effected by the contractions of the 

 contractile vesicle. But if this were the case, the movement 

 must always take place in a direction opposite to the vesicle, 

 a circumstance which I have not observed. 



[To be continued.] 



