GENUS HYALODISCUS— HTALODISCUS RUBICUNDUS. 95 



movements the red mass underwent more or less change of shape, the sur- 

 face at different points would rise and fall, and here and there the pointed 

 processes would be withdrawn and others would be projected. The band 

 of ectosarc also moved in a wave-like manner, extending and receding in 

 different positions. 



The red mass of endosarc was composed of a basis of fine red granules 

 with a few larger ones of the same color but darker, and a few scattered 

 oil-like molecules. The central portion of the endosarc, from time to time, 

 exhibited a clearer circular spot, apparently indicating the presence of a 

 nucleus. There were also to be seen two or three small vacuoles, but I 

 failed to detect any movement in them. 



Another specimen, found at the same time with the preceding, repre- 

 sented in fig. 18, was about half the size. It was of the same color, but 

 the endosarc contained a multitude of conspicuous globular colored corpus- 

 cles mingled with the finer granular basis. The clear colorless ectosarc 

 extended around the border of the colored endosarc, and projected a few 

 conical processes, into which none of the colored granular matter of the 

 latter readied. The movements of the animal were of the same character 

 as in the former specimen. 



Plakopus ruber, described by Prof. Schulze, is probably identical with 

 Hyalodiscus rubicundus, as suspected by this author, though it is a very 

 much larger animal, and contains several nuclei. Prof. Schulze gives as 

 the size of the former from 0.2 to 0.6 mm. 



DIFFLUGIA. 



Latin, diffluo, to flow. 



Difflugia : Leclerc, 1815. Arcella: Ehrenberg, 1841. Lecquereusia : Schlumberger, 1845. Bomceochlamys ; 

 Heterocosmia ; Exassula: Ehrenberg, 1871. 



Shell very variable in shape, usually composed of extraneous angular 

 particles of hyaline quartz-sand, sometimes mingled with other bodies, such 

 as diatom-cases, sponge-spicules, etc.; the same forms sometimes composed 

 of chitinoid membrane incorporated with scattered extraneous particles or 

 composed in part or entirely of intrinsic particles of peculiar character. 

 Mouth inferior, usually terminal, rarely sub-terminal. Sarcodic mass com- 

 monly occupying the greater part of the capacity of the shell, attached by 

 threads of ectosarc to the interior of the fundus and sides, and by a pro- 



