374 MRS. L. J. VELET — CONTfilBUTION TO THE 



A further Contribution to the Study o£ Pelomyxa palustris 

 (Grreeff). By Lilian J. Velbt {nee Goulb), F.L.S. 



[Read 6tli April, 1905.] 



(Plates 36-38, & text-figure.) 



The freshwater Ehizopod JPelomyxa palustris was first described 

 by Professor GreefF in 1867 as Pelohius and later discussed by 

 the same observer under its present name. 



Between 1869 and 1879 his research.es were followed by tbose 

 of Leidy and Korotneff". In 1891, Prof. A. G. Bourne studied 

 another species (P. viridis) and published his observations on 

 this and the species in question in the ' Quarterly Journal of 

 Microscopical Science.' Prof. Biitschli, in 1892, contributed to 

 our knowledge of the structure of the protoplasm in Pelomyxa ; 

 and later observers, notably Dr. Penard in 1893 and since, have 

 published observations of great interest relating to this curious, 

 and in some respects mysterious, Protozoon. The present 

 writer, in a paper published in the ' Quarterly Journal of Micro- 

 scopical Science' in 1894, brought forward some points with 

 regard to the minute structure of Pelomyxa palustris, together 

 with some new observations confirming, as far as they went, the 

 suggestions of Prof. Bourne and Dr Penard that the rods found 

 scattered through the protoplasm of Pelomyxa were neither 

 crystals nor protein crystalloids, as had been previously supposed, 

 but bacteria. Mr. M. D. Hill undertook some culture-experiments 

 with a view to establishing this, but these had negative results. 



The view that the rods are bacteria has, however, found 

 general acceptance, though no absolute proof has yet been 

 published. In Dec. 1895 an opportunity offered itself to me for 

 the further study of this and other questions I'elating to 

 Pelomyxa ; investigations were then undertaken, and have been 

 continued at intervals each year up to 1903. The results of 

 these investigations are embodied in the present paper, and the 

 new points which it is hoped thereby to establish, with regard 

 (1) to the bacteria, (2) to the refringent bodies, (3) to the general 

 structure and behaviour of the animal itself, are, mainly, as 

 follows : — 



