TRICHOMONAD FLAGELLATES. 297 



are shown the protean changes undergone by a single active vegeta- 

 tive individual in the course of about fifteen minutes while entrapped 

 in a viscous debris from the intestine but not adherent to the substrate. 

 The changes include the formation, but not detachment, of small 

 (Fig. C, 2) and large (Fig. C, 8) posterior blobs, the shifting of the 

 main cytoplasmic enlargement from the anterior to the posterior end 

 and back again (Fig. C, 5-9), and the protraction and retraction of 

 posterior pseudopodia. These facts seem to preclude the existence of 

 anything like a rigid pellicle, though Kuqzynski (1914) describes a 

 peripheral layer staining a light pink in Giemsa, and speaks of skeletal 

 fibrillae which are "ganz schwach angedeutet" but does not figure 

 them. We have found no structural evidence of such a pellicle except 

 the more homogeneous texture of the surface layer, and the line about 

 the cytostome, and none whatever of the "skeletal fibrillae" in this 

 layer. 



Scattered throughout the cytoplasm are many spheroidal vacuoles 

 which move about, not by regular and continuous cyclosis but in 

 adjustment to the protean changes in form. They appear to be food 

 vacuoles or at least to be concerned in metobolism. Their contents 

 is a homogeneous highly refractive fluid and in life they obscure all 

 other structures more or less. We have not seen evidence of their 

 formation at the bottom of the cytostome nor of any circulation or 

 discharge. There is no constant differentiation in different regions 

 of the body. They vary in diameter from 0.5 to 4 fx, the larger vac- 

 uoles being found in the rounded up individuals in the prophase. 

 Compound vacuoles are occasionally seen. 



In a few cases (PI. 3, Fig. 33) rod-like structures resembling bacteria 

 have been found in elongated food vacuoles, but beyond this there has 

 been no evidence that this species takes in solid food. Other species of 

 Trichomonas such as T. batrachorum, T. muris, and several as yet 

 undescribed species in our material, generally have solid particles and 

 bacteria in at least some of their food vacuoles. This absence of food 

 particles is also in sharp contrast to the condition in Tctratrichovionas 

 prowazeki (Alexeieff) which actively engulfs bacteria and other organic 

 material, and crowds its food vacuoles with such substances. 



The vacuoles of individuals treated with a trace of methylene blue 

 N are not stained at all but small spheroidal granules in the cytoplasm 

 between the vacuoles stain (Fig. D, 2) diffusely and the animals die 

 within an hour. In dilute Janus green the nucleus, blepharoplast, 

 and chromatin granules in axostyle and cytoplasm stain quickly and 

 the animal dies in a few moments. 



