STUDV OP PI'ILOMrXA PALUSTH13. 389 



solutions of egg-albumin without mud, they lived well and 

 divided — a result which might cut both ways. 



If, however, the bodies act as a reserve food-supply to 

 JBelomyxa^ it must be a distinct disadvantage to the animal to have 

 an almost unlimited number of bacteria drawing upon the same 

 supply, and thus we should be left without any explanation of 

 the relation of the bacteria to the animal. It would also be 

 inexplicable that Pelomyxa should constantly eject refringent 

 bodies, as it normally does. 



(2) A second view, viz., that the refringent bodies are a waste 

 product of metabolism, useless to the animal, seems, therefore, 

 more tenable. In such a case the presence of the bacteria would 

 be perfectly explicable, as they would be of direct advantage to 

 the animal in clearing off useless products, while the proved 

 ejectment by Pelomyxa of the bacteria, when the branching 

 system became so large and rigid as to be inconvenient, would 

 also be an advantage to the bacteria, in enabling them to scatter 

 their swarmers so as to be ingested by fresh hosts with the mud 

 of their habitat. 



The condition of the resting or quiescent Pelomyxcs, which 

 had filled themselves up with sand, described in my previous 

 paper, is very consistent with this view ; for in some of these the 

 refringent bodies were very few and very small, and in others 

 practically non-existent, and the bacteria were equally scarce. 

 This suggests that metabolism not being then active, no waste 

 products were being formed and no scavengers were required ; 

 of coiirse it might also mean that the reserve supply ha(^ been 

 already exhausted, but if that were the case it is difficult to 

 imagine what the animal could subsequently have been living 

 upon. 



Taking all the circumstances into consideration, the vievr of 

 the writer is that the refringent bodies are waste products of the 

 metabolism of Pelomyxa, and that they serve in a double sense 

 for the support of the symbiotic bacteria. 



The Animal as a whole. 



Several points of interest as to the general behaviour of 

 Pelomyxa palustris were brought out in the course of these 

 investigations : the first of these refers to the character of the 

 pseudopodia, which are generally described as lobose and blunt. 



LTN-N. JOURX. — ZOOLOGY, VOL. IXIX. 27 



