ACTIXOPIIRYS. 45 



their presence, they possess a power not only of extending to 

 a great length, but also of rendering themselves so rigid that a 

 few of them can sustain the whole weight of the body. As a gen- 

 eral thing they project from the body in perfectly straight lines, 

 and move so slowly as to appear like stiff bristles, rather than 

 what they really are. 



By a close and patient examination, however, one is not long 

 in coming to a conclusion that these apparently sluggish creat- 

 ures are not only animals, but at times very active and power- 

 ful. These particulars are better understood when the intimate 

 structure of the Actinophrys is under consideration than by any 

 other process of observation. We will therefore proceed to in- 

 vestigate the basis of its organization, as it is exhibited in its 

 cellular tissues. The most comprehensive view of its structure, 

 that it is desirable to take, is that in which we get what is called a 

 sectional view, as if a section of the body, next the eye, had been 

 cut away and the interior exposed to the sight. This is done by 

 placing the glasses of the microscope so as to get a view of the 

 interior, whilst all those parts nearer to the eye are out of focus, 

 and consequently not defined so as to form a distinct picture. 

 The figure before us is a sectional view, so deep that the body 

 is as it were cut into halves. By it we get an insight of the re- 

 lations of the cells to each other, and to the pseudopodia; in fact 

 every part of the organization may be seen at a glance. Under 

 a low magnifying power the body appears as if it were a mere 

 globule of gum-like or mucous matter, with numerous closely set 

 cavities hollowed in its substance ; but a closer examination, 

 with good lenses of a higher power, will detect a distinct cell- 

 wall about each cavity. Where the cells lie close together the 

 neighboring walls appear as one ; but at other points, which are 

 numerous, the cells are separated by the interstitial mucous sub- 

 stance, (cytoblastema, cell-generator,) and there the wall may be 

 seen to have a very appreciable thickness. This is a very im- 

 portant point to determine, because by this feature alone the 

 Actinophryians are to be estimated as more highly organized 

 than those groups, the Rhizopods and Sponges, which possess a 



