S36 THE AMERICAN MONTHLY [October, 



with fluid, across which threads of protoplasm stretch from the 

 centre to the fine fihii of protoplasm which lines the shell. This 

 latter feature much resembles the cells of many plants and will 

 also be seen in JVoctiluca, and it obviously economizes protoplasm 

 and makes greater bulk possible. Here as in Difflugia the 

 pseudopodial protoplasm is located at one end of the body and 

 nucleus and contractile vacuole are within. It is here noticable 

 that these three genera cannot so readily be understood as in a 

 single series, Hyalosphenia being derived from Difflugia, as they 

 can be understood as in two series, both starting from Amoeba. 

 In its chemical nature the covering of Hyalosphenia is interest- 

 ing, being albuminoid and less unlike the chemical nature of 

 compounds in the protoplasm than are the skeletons of lime or 

 silica found in Rotalia^ Actinosphceriji?n^ and many other more 

 specialized Rhizopods. It is therefore a less specialized act of 

 the secretory power to produce a chitinous than a calcareous or 

 siliceous skeleton. 



Actinosphaerium eichorni (fig. 7) is found very abund- 

 antly with Amoeba and Diftiugia.* 



Clathrulina elegans (fig. 8) is stalked, a horny stem sup- 

 porting a hollow horny spherical basket with lai-ge openings. 

 Within the basket lies a ball of protoplasm, and from this, through 

 the openings, long delicate filaments of protoplasm stretch. There 

 is no radial skeleton. 



Lieberkuhnia (fig. 13) is a naked body of rather definite out- 

 line, with one end prolonged into pseudopodia. The pseudopodia 

 are never strictly radial, but are branching, the branches lead- 

 ing out into finer and finer divisions which often anastomose or 

 join together. The food is caught upon the network of psuedo- 

 podia and digested there. 



Gromia oviformis (fig. 11) has a membraneous saccular 

 skeleton imbedded in and surrounding the protoplasm which, as 

 in Lieberkuhnia^ is drawn out into the form of long filiform 

 pseudopodia which anastomose frequently but are somewhat 

 radial and lack radial supporting skeletons. 



Rotalia has a calcareous spiral chambered shell. The proto- 

 plasm is placed within the shell, by which it is protected, and fil- 

 amentous pseudopodia are thrust out through minute holes which 

 perforate the lime. The pseudopodia often anastomose. In 



* It need not be difficult to find material for demonstrating many of these points. Very often 

 material which at first seems barren will be found after standing a few days in a quiet dish in 

 the laboratory to furnish abundance of many genera of Protozoa. It presents a central spher- 

 ical mass ot protoplasm which is so much vacuolated as to appear like a mass of bubbles. On 

 each side is a contractile vacuole. The protoplasm extends in fine radial threads of the ex- 

 tremest tenuity and constantly circulates out and back along the threads and through the cen- 

 tral part of the body. To support this delicate mass a shell of silicate is secreted by the proto- 

 plasm from the surrounding water; the shell consists of an internal frame-work and many radii. 

 In this creature we find the secretory powers noticed in Hyalosphenia still more highly special- 

 ized, and the same is true of the vacuolation. Such pseupodia as those oi Avia'ba firoteus are 

 wanting, but the radial protoplasmic threads are comparable with pseudopodia and are more as 

 in A. radiosa, though far finer. With Actinosphierium we reach an order of many families and 

 genera, great variety of form and situation, many marine, but all despite their immense diver- 

 sity easily reducible through Actinosphaerium and Hyalosphenia to the Anireboid type. 



