212 M. E. Claparede on Actinoplirys Sol. 



pears circular, but its general form is spheroidal, witli a great 

 number of radiating processes, which are sometimes very long. 

 No distinct nucleus is to be recognized. What Kolliker describes 

 under this name scarcely deserves to be so called, for this sup* 

 posed nucleus passes gradually into the general substance of the 

 body, as indeed Kolliker himself ])erceived. Apparently the sub- 

 stance of the body becomes condensed by degrees towards the 

 centre or in the opposite direction, producing a diflference in 

 appearance between the central and peripheral parts. The names 

 "inner layer" and "outer" or "cortical layer" are therefore 

 preferable. From time to time a globular prominence rises 

 slowly and gradually from a particular point on the surface of 

 the animal (tig. 1 o) ; this increases more or less in different 

 cases, sometimes, especially in small individuals, attaining nearly 

 a third of the size of the entire body, but generally reaching only 

 ^th or j'^th of that size. The margin of this projection is 

 always well defined, much more so than the other parts of the 

 body, especially when it has attained its greatest evolution. At 

 this moment it contracts suddenly and disappears entirely, so 

 that a flattening of the outline is often to be observed at the 

 point previously occupied by this remarkable elevation ; the 

 margin soon becomes rounded again, the globular projection 

 gradually rises, attains its previous highest development, and 

 then suddenly disappears again. 



At first I felt inclined to adopt Ehrenberg^s statements as to 

 the presence of a mouth in Actinophrys, as the description of 

 the so-called proboscis agreed exactly with my own observations, 

 especially as Kolliker had entirely overlooked this peculiar 

 phajnomenon, and his descriptions of the mode in which the 

 animal eats did not appear to me to be quite clear. In fact this 

 regular protrusion and contraction of the proboscis, as Ehrenberg 

 called it, rendered the admission of foreign bodies into the sub- 

 stance of the Actinophrys far more intelligible than the mode of 

 inception supposed by Kolliker, by the mere pressure of the 

 processes*. But if this organ were not a proboscis in Ehren- 

 ber"-'s sense, nothing appeared to me more natural than to con- 

 sider it as a contractile vesicle, on account of its regular con- 

 tractions, especially as this view was supported by Prof. J. 

 Miiller. 



This opinion, however, is not new ; it has already been put 

 forward in Von Siebold's 'Comparative Anatomy,' but has not 

 been referred to by the generality of observers. Siebold says, 

 " In this respect (the contractile vesicle), Actinophrys Solh very 

 remarkable ; its contractile vesicles are situated so close under 

 the general integument, that the fluid flowing to them from the 

 * Kolliker, Ueber Actinophrys Sol, Zeitschr. fur "Wiss. Zool. 1849. 



