481 PROFESSOE E. RAY LANKESTER. 



LiTHAMCEBA DISCUS, nov. geii. et sp., one of the Gymnomyxa. 

 By E. Ray Lankester, F.R.S/ (With Plate XXllI.) 



I INCLUDE under the division Gymnomyxa all those Pro- 

 tozoa or Homoblastic animals which expose, in a naked state, 

 to the medium in which they live, the living protoplasm of 

 their body-substance, in the form of those lobose, filamen- 

 tous, or reticulate processes known as pseudopodia. The 

 group is the complement of the Corticata, in which a perma- 

 nent difierentiation of the surface of the body-substance 

 has been effected, necessitating either parasitic nutrition 

 (GregarinseJ or the specialization of an ingestive orifice (the 

 Ciliate, Flagellate, and Suctorial Infusoria). The Gymno- 

 myxa thus include, together with the Radiolaria and others, 

 all those forms known as Rhizopoda, whether provided 

 with nucleus or devoid of that structure. 



In examining a gathering from a pond near Birmingham, 

 forwarded to me in April last by Mr. Bolton of that town, 

 I observed six specimens of an organism belonging to the 

 group of the Gymnomyxa, apparently hitherto undescribed. 



The organism in question is related to the Amoebae, having 

 the coarse, lobose pseudopodia characteristic of that genus. 

 At the same time the protoplasm of which it consists is 

 vacuolated in a remarkable way not observed in Amoeba, and 

 moreover, numerous peculiar concretions are embedded in 

 its substance, which are not precisely like anything known 

 in Amoeba. The actual form of the processes of the body- 

 substance or pseudopodia extruded by the present form is 

 also not identical with that of the pseudopodia of the com- 

 moner Amoebse, such as A. princess or A. racf/o^a, but rather 

 resembles the hernia-like extrusions of the protoplasm ex- 

 hibited by that very remarkable example of the freshwater 

 Gymnomyxa, Pelomyxa, described a few years since by 

 Professor Greef, a form which I have had the good fortune 

 to find also in this country. 



The new Protozoon I propose to call Lithamoeha discus, 

 the generic name having reference to its characterstic con- 

 cretions, and the specific name to the form which it assumes 

 when in a quiescent condition. 



I am not able to furnish any particulars as to the life- 

 history of Lithamoeha discus, but it appears to me that the 

 details of its structure are sufficiently interesting to merit 

 publication. 



Form of the body. — In Plate XXIII, fig. 1, a specimen is 



