462 ORIGINAL ARTICLES. 



II. — In Actinoplirys and its allies there is a degree of definiteness 

 in the form and arrangement of the pseudopodia, which contrasts 

 strongly with the entire indeiiniteness which prevails throughout the 

 Eeticulose order. These organs are, for the most part, simple fila- 

 ments, tapering gradually from base to point, usually maintaining 

 their isolation throughout, and extending in a radiary direction from 

 the body of the animal. It is obvious that they are of much firmer 

 consistence than in Gromia and its allies, since they neither sub- 

 divide themselves by ramification into finer filaments, nor do they 

 show any readiness to coalesce when they come into mutual contact. 

 Still it is equally certain that they can be retracted into the general 

 mass of the body, and fused (as it were) into its substance ; and such 

 a fusion takes place when food is being entrapped by their means. 

 A careful examination of the substance of the Actinophrys serves to 

 explain this apparent inconsistency ; for it thence appears that the 

 body and its pseudopodian extensions are far from having the homo- 

 geneousness of those of Lieberkiihnia, but that there is an incipient 

 differentiation of their substance into two dissimilar constituents, the 

 outer layer being least granular and of firmer consistence, whilst the 

 contained portion approaches more nearly to the character of a liquid, 

 as may be seen by the freer movements of the granular particles which 

 are suspended in it. These two constituents have been appropriately 

 designated by Dr. T. Strethill "Wright as the "ectosarc" and the 

 " endosarc." There is no definite line of demarcation between them; 

 but the one graduates insensibly into the others. It seems to be, 

 however, from the ectosarc alone that the pseudopodia are put forth ; 

 the granular endosarc not extending itself into them. A movement 

 of granules along their surface may indeed be discerned by careful 

 observation ; but these appear to be merely particles which have been 

 entrapped by adhesion to the surface of the pseudopodia, and are 

 being transmitted to the body; and there is nothing like that regular 

 circulation from the body to the extremities of the pseudopodia, and 

 back again, which is so remarkable a feature in the Reticularia. With 

 the incipient differentiation of the protoplasmic substance, there seems 

 to be associated the presence of a " nucleus ;" which, however, is not 

 so strongly marked in Actinophrys as it is in Amoeba, and may easily 

 escape notice. The " contractile vesicle," on the other hand, is always 

 discernible, and its actions are very regular. Its presence may be 

 considered as superseding the necessity of the general protoplasmic 

 circulation ; since it can scarcely be doubted that its function is to 

 maintain a continual movement of nutritive fluid among a system of 

 channels and vacuoles excavated in the substance of the body, some 

 of the vacuoles which are nearest the surface being observed to 

 undergo distention when the vesicle contracts, and to empty them- 

 selves gradually as it refills. 



The general characters of Actinophrys, with a more or less com- 

 plete limitation of the pseudopodia to one portion of the body, 

 necessitated by its enclosure within a membranous or chitinous 



