GENUS DIFFLUGIA— DIFFLUGIA SPIEALIS. 127 



A singular variety is represented in figs. 14, 15, in which the shell is 

 composed of narrow plates or rods mostly in small parallel groups of twos 

 and threes or more, and laid closely together in every direction. This is 

 probably the kind to which Schlumberger refers in his account of Lecque- 

 reusia jurassica, in which he says the shell is composed of a paste of minute 

 bacillar bodies. 



Small forms of Difflugia spiralis are not uncommon in which the shell 

 is composed of transparent chitinoid membrane incorporated with variable 

 proportions of linear bodies, diatoms, and sand particles, as represented 

 in figs. 16-22. 



A curious specimen, of large size, represented in fig. 23, was composed 

 of irregularly rounded or oval bodies containing a central nucleus. The 

 nature of these bodies I did not determine. 



The sarcode of Difflugia spiralis is colorless, independently of the color 

 given to the endosarc from the presence of food. In the more translucent 

 specimens it can often be detected as a spheroidal mass of variable size 

 occupying the body of the shell, with a narrow neck passing off from 

 one side, in a retort-like manner, and extending through the aperture of 

 the partition, and thence gradually widening to the mouth. The food 

 usually gives to the endosarc a yellowish or pale brownish hue, which is 

 sometimes mingled with green and other colors. The pseudopods in num- 

 ber, form, and changes, are of the same character as in other species of 

 the genus. 



The size of Difflugia spiralis ranges from the ^th to the ^th of an 

 inch. 



Difflugia spiralis may be regarded as the oldest known species, and, as 

 previously intimated, was described and figured by Leclerc in 1815. He 

 represents two varieties ; one in which the shell is composed of quartz-sand, 

 the other in which it appears to be composed of chitinoid membrane. He 

 also represents two individuals united, mouth to mouth, in the condition 

 usually indicated as that of conjugation. 



Perty describes and figures the same species, but regards it as a mon- 

 strosity of Difflugia piriformis, in which view he is sustained by Dr. Wallich. 

 I can see no reason why Difflugia spiralis should be considered a monstrosity 

 any more than any other recognized form of the genus. 



Difflugia spiralis is a common species, but I have found it especially 



