24 ILLINOIS BIOLOGICAL MONOGRAPHS [234 



and I have never been able to demonstrate the presence of threads in a 

 freshly opened intestine. The medium must then be other than the nor- 

 mal digestive juices. It thus seems possible that no strands are present 

 in the normal condition but that they harden only after being for some 

 time in an unnatural medium. Instead of hardening and condensing in 

 the host, the constituents of the secretion are probably dissolved in the 

 digestive juices as fast as formed. 



As the reason for the presence of the semi-gelatinous secretion from 

 the body, I accept the view of Porter which states that movement is 

 probably caused by a very slight undulatory motion of the under sur- 

 face of the animal. Just as Limax moves forward by a slight ventral, 

 and dorsally imperceptible, muscular movement in a vertical direction 

 on an underlying surface the friction of which is caused by the secretion 

 of a sticky mucus, the gregarine moves forward by imperceptible ver- 

 tical movements in the myonemes on that side of the body which hap- 

 pens to be ventral at the time, friction being produced with the under 

 surface by the exudation of mucus from the body. That there is a se- 

 cretion from the whole body and not only from the posterior region is 

 demonstrated by carmine which adheres in fine particles to all parts of 

 the animal. 



It was shown by Schewiakoff that there are tiny pores between the 

 longitudinal ridges. These probably serve as exits for the secretion. 

 The longitudinal ridges carry it backward and away after it has served 

 its usefulness in effecting motion. The secretion is in the form of 

 threads simply because it is constricted into narrow lines by passing 

 backward between the tiny ridges. The threads are not necessarily con- 

 tinuous but may be often broken. 



Thus I am of the opinion that the secretion at the posterior end of 

 the body does not produce motion, but that it is a waste product by the 

 time it has reached this end ; it is likewise effective as shown above in in- 

 hibiting motion in an unnatural medium, as well as in producing it. 



Besides the simple progressive movement, a twisting or bending 

 movement is commonly observed. The body bends often with little or 

 no change of position. This bending involves chiefly the anterior half 

 of the deutomerite. The protomerite is turned from side to side like the 

 head of a higher animal while the parasite is progressing from place to 

 place. The protomerite, of itself, apears however to be incapable of 

 movement and not the slightest change in form has been noticed. The 

 region of greatest capacity for motion is the anterior end of the deuto- 

 merite. The endocyte of this region flows out into small pockets made 

 in the elastic epicyte and as a group of two or three small outpushings 

 is made on one side, close together, the protomerite falls to the opposite 

 side. An outpushing of several small pockets just below the bent over 



