ANIMAL MICRO-PARASITES. 597 



Here and there, possibly from injury or want of development, the 

 spine-like process appears to be blunted or absent. By very careful 

 focussing on the upper edge of the central portion, the author 

 discovered the existence — much more markedly in some of the 

 parasites than in others — of a longitudinal membrane with either 

 a straight or undulating margin. The membrane is attached along 

 the body, arising from the base of the rigid filament, and becomes 

 directly continuous at the opposite end with the flagellum. In some 

 cases the edge only is deeply stained, giving the appearance of a 

 thread continuous with the flagellum, so that one might be easily 

 led to overlook the membrane, and imagine that the flagellum arose 

 from the opposite end of the body, at the base of the spine-like 

 process. 



Close to the base of the spine-like process a clear unstained spot 

 is in many parasites easily distinguished ; and at the opposite end 

 there is, in some, the appearance of the deeply-stained protoplasmic 

 contents having contracted within the faintly-stained membranous 

 investment. When the longitudinal membrane has a wavy outHne 

 the undulations are much more marked in some cases than in others. 

 Here and there the wavy outline appears first on the one .side of 

 the central portion and then on the other ; but there never is any 

 waving outUne on both sides of the same part of the body, and this 

 was explained by a careful examination, which showed that the 

 somewhat ribbon-hke parasite had become doubled on itself. The 

 discovery of this undulating membrane at once suggested to the 

 author an explanation of the lateral pseudopodia described by 

 Evans. If we imagine that we are looking down upon the parasite, 

 with the edge of the membrane towards us, one can conceive that 

 the rapid undulations, first on one side and then on another, 

 might give an image upon the retina which could be construed 

 as due to the protrusion of lateral pseudopodia. In stained 

 preparations no trace of the circlet of pseudopods could be 

 discovered, and the undulating membrane may account for this 

 appearance also. 



Owing to the somewhat curved and twisted shape of the parasite 

 and the curling of the flagellum in the stained preparations, it 

 was difficult to make exact measurements ; but the average width, 

 according to whether the membrane was visible or not, varied from 

 1 to 2 /x, and the length of the body from 20 to 30 fi. The flagellum 

 was about the same length as the body. 



Here and there in a stained preparation there were the forms 

 already described by Evans resulting from the fusion of two para- 



