128 FRESH- WATER RHIZCXPODS OF NORTH AMERICA. 



abundant in the ponds of sphagnous and cedar swamps in New Jersey, 

 where it is also to be obtained, in the greatest variety of form, in association 

 with D. piriformis, D. urceolata, etc. The habits and food are the s^me as 

 in other species generally. 



I have occasionally observed two individuals of Difflugia spiralis 

 applied together, mouth to mouth, in the manner first described and figured 

 by Leclerc, and as represented in fig. 3, pi. XIX. This condition I have 

 not been able to discover leading to any important result, and I may say 

 the same of other species of Difflugia seen in conjugation. 



In one instance I saw two small individuals applied to the mouth of a 

 third and larger individual, and in another instance I saw three small 

 individuals in like manner applied to a larger one. 



In the instance represented in the figure, on focusing the conjugating 

 pair so as to see the contents, they were observed to flow from one to the 

 other and back again. After about half a dozen repetitions of the flow and 

 ebb, the contents, apparently equally divided in the two shells, remained 

 quiescent for a time, and then the two individuals separated and moved 

 away in the usual manner. The construction of the shell prevented the 

 determination of any change within, even if such had taken place. 



HYALOSPHENIA. 



Greek, hualos, crystal; sphen, a -wedge. 

 Hyalosphenia: Stein, 1857. Difflugia: Tatem, 1870. Catharia : Leidy, 1874. 



Shell compressed ovoid to pyriform, composed of transparent structure- 

 less chitinoid membrane; mouth terminal, inferior, transversely elliptical. 

 Sarcode mass occupying the interior of the shell to a variable extent, 

 attached to its inner surface by divergent threads and also connected to the 

 border of the mouth; composed of pale granular protoplasm mingled with 

 colorless or colored corpuscles, or both together. Nucleus large, and cen- 

 trally situated in the fundus of the sarcode. Contractile vesicles several, 

 occupying a position between the former and the periphery of the fundus. 

 Pseudopods few, digitate. 



