1905.] NATURAL SCIENCES OF PHILADELPHIA. 95 



dice the decision, it is advisable to see if an explanation may not be 

 had along different lines. 



The formation of pseudopodia in rhizopods is due to movements 

 of the endosarc, and in gregarines the endosarc is evidently mobile. It 

 may therefore be suggested that the polymorphism of certain of the 

 Polycystidea is caused in the same way as it is in Rhizopoda. An 

 endoplasmic flow, if by chance it were directed radially, would evidently 

 result in such protrusions as are actually seen in Trichorhynchus. For 

 it is to be remembered that such forms have a thin, extensible ectosarc, 

 which would offer little resistance to such a flow. The difficulty in 

 arriving at a decision is that the endosarc of most polycystids is so 

 opaque that flowing movements might take place without it being 

 possible to detect them. As I have already stated, the little gregarine 

 of Lithobius is the only species at all favorable for a study of this 

 element which has yet come under my notice. 



In the Monocystidea, however, the conditions are more favorable. 

 Flowing of the endosarc is a matter of common observation, and it has 

 generally been taken to be the cause of their polymorphism. While 

 this may be so, my own observations on monocystids lead me to ques- 

 tion it. These were made on a species of Diplocystis, a parasite of 

 Allolobophora longa. This gregarine has the form of a serpent. In 

 the cases observed movements were constant. There would appear 

 at any point of the body a swelling which passed rapidly either forward 

 or backward. The endoplasm fills this swollen part, flowing into it 

 in front and out of it behind. Two such swellings may arise simul- 

 taneously and, advancing toward each other, amalgamate. The large 

 swelling thus produced would maintain a fixed size for a moment, and 

 then from its central part two streams would start in opposite direc- 

 tions, and the swelling would rapidly disappear. In one case the 

 peripheral granules in a swelling moved along with it, while those in 

 the centre moved in the opposite direction. 



An individual of this species was observed to burst,' permitting the 

 escape of a portion of the granular contents. The ectosarc thereupon 

 contracted, and showed very plainly a series of strise, parallel and 

 spirally disposed. Evidently these stria were the expression of a 

 powerful myocyte. 



Contractions of the myocyte would produce a flowing of the endo- 

 plasm; flowing of the endoplasm would result in extensions of the 

 limiting layer. Hence, on purely a priori grounds, the one explanation 

 has as much claim to consideration as the other. In the case of the 

 phenomena just described, however, it seems far more reasonable to 



