231] STUDIES ON GREGARINES— WATSON 21 



elements in this myocyte has since then been assigned as the basis for the 

 bending movements of Gregarines. 



The first explanation for the gliding movement was offered by Sche- 

 wiakoff (1894) who supposed a gelatinous secretion from the posterior 

 end of the body formed a stalk and that as the animal secreted new addi- 

 tions to this stalk it pushed itself forward by the same amount. 



Porter (1897) probably without knowledge of Schewiakoff's theory 

 proposed the following hypothesis : 



"It [locomotion] is a 'very slow movement of translation in a straight 

 line' without any apparent contraction of the walls of the body. It is 

 probably caused by a very slight undulatory motion of the under surface 

 of the animal." 



Crawley (1902:420; 1903:57), unaware of Porter's hypothesis, 

 came to the same conclusion that an undulatory movement on the under 

 side of the body is the basis for locomotion ; and he disagreed with Sche- 

 wiakoff's explanation. 



My observations on movement in Gregarines have been chiefly con- 

 fined to the species Leidyana erratica of the family Gregarinidae because 

 of its activity and the readiness with which material is obtained. 



In the normal intestinal juices of the host when the intestine is first 

 opened, practically none of the animals are in motion ; they lie rather in 

 inert masses from which the name Gregarine is derived. Since the juices 

 rapidly evaporate and cannot be secured from other animals in sufficient 

 abundance to observe normal movement over a considerable portion of 

 time, artificial media must be used, the most common being distilled water. 

 This causes the animals to disintegrate after periods varying from fifteen 

 minutes to three or four hours, depending on the age of the parasites and 

 their consequent ability to adapt themselves to a change in external pres- 

 sure. The young, fragile animals disintegrate rapidly; the oMest often 

 resist the change in external pressure for several hours. When an epi- 

 merite is present on a free individual, it is quickly ruptured in water. 



Egg albumen is not a satisfactory medium in which to observe mo- 

 tion, for the parasite has great difficulty in ploughing its way through 

 the thick substance. Rupture of the walls is prevented by its use because 

 of a similarity in density between the animal protoplasm and this 

 medium. 



Various acids in 0.5% solution were used and their effects on motion 

 noted, among them being hydrochloric,nitric,acetic,sulphuric, and tannic. 

 All of them killed the animals very quickly and caused the protoplasm to 

 collect in masses ; the epicyte was also often ruptured. Chloroform and 

 sulphuric ether in 0.5% solutions produced no apparent structural 

 changes but the parasites were quickly anesthetized. 



