48 BULLETIN: MUSEUM OF COMPARATIVE ZOOLOGY. 



Freozel is especially important, because it gives a careful account of the 

 structural conditions of the genus studied by him, though even he did 

 not make use of sections to ascertain the minuter details of structure. 



At the suggestion of Dr. Mark, I began in the autumn of 1895 an 

 investigation of this peculiar and interesting parasite of Termea flavipes, 

 in the hope of being able, by means of more recent methods, — especially 

 sectioning, — to add something to what was already known concerning 

 them. An excellent 1.5 mm. homogeneous immersion by Zeiss has been 

 of much value to me in studying the minute details of structure. In 

 October I captured some of the White Ants, both •' workers "■•^nd 

 " soldiers," in the woods near Cambridge, and on opening the intestine 

 of one of them found it swarming with the same kinds of parasites that 

 Leidy had discovered in his New Jersey Termites. 



1. Trichonsonpha agilis. 



Plate 1: Plate 2 ; Plate 3, Figs. 24-86. 



I have represented in Figures 1 and 2 what seem to me fairly normal 

 and characteristic appearances of a quiescent T. agilis, and in Figure 3 a 

 view of the head end, seen from the anterior pole. My figures should 

 be considered, however, simply as in a measure supplementary to those 

 of Leidy. His observations were so careful and accurate that I have 

 almost no modifications or corrections of his description to suggest ; but 

 I shall be able to add something to his account. 



Upon seeing one of these peculiar animals, the question immediately 

 arises. Wherefore such a remarkable cloak of cilia 1 Well developed 

 locomotor organs are the last thing one would expect to find in a para- 

 site whose food is close at hand and whose field of exploration is so 

 limited. With the hope of getting some light on this question, and 

 wishing at the same time to discover, if possible, the situation of 

 the mouth, I experimented by putting living specimens into various 

 fluids ; among others, into very much diluted milk. The Tricho- 

 nymphfe immediately on escaping from the intestine began ploughing 

 their way through the milk corpuscles, passing across the field of the 

 microscope so rapidly that, in order to follow them, it was necessary to 

 keep the slide in constant motion. The various courses traversed by 

 them were indicated by paths cleared of the oil globules. Upon watch- 

 ing their movements, it presently became apparent that the shortest and 

 most anterior cilia were to a very large extent responsible for the mo- 

 tion. The longer cilia, those extending backwards to about the region 



