630 SUMMARY OF CURRENT RESEARCHES RELATING TO 



mentary canal to the blood-vessels) is played by the leucocytes, an 

 hypothesis confirmed by the occurrence of Haemocytozoa or parasites 

 within the red blood-corpuscles, while within the leucocytes bodies 

 are not unfrequently observed which resemble parasitic germs. 



I. Trypanosoma sanguinis Graby. This Flagellate was found in 

 as many as six varieties in the blood of frogs and fishes. The cha- 

 racteristic undulating hyaline membrane, prolonged into a flagellum, 

 displayed various degrees of differentiation. All Trypanosoma 

 species exhibit screw-like undulating movements and contractions. 

 In the frog the following four varieties are distinguishable: (1) the 

 simple membranous form, in which tho flat extremely mobile body 

 passes without visible boundary into the membrane ; (2) the rolled- 

 up form, having a filter-like shape, resulting from the helicoid 

 twisting of the body on its transverse axis; the undulating membrane 

 extends along the superior broader margin ; (3) the " flat-spiral " 

 form, having a somewhat compressed long conical body, pointed 

 posteriorly and spirally twisted ; the undulating membrane only 

 along the anterior broader flattened end ; (4) the " comb-like spiral " 

 form, twisted in a more or less complete longitudinal spiral, with the 

 surface of the pear-shaped body like a Pecten shell ; the narrow, 

 well-differentiated undulating membrane along one margin or in the 

 cleft between the two approximated margins. If the two margins of 

 the leaf-like body are fused there is, of course, no cleft ; the mem- 

 brane arises from the anterior broad end, and a most beautiful 

 " cornucopia " form results. 



These varieties of Trypanosoma (Undulo-Flagellata) were not 

 observed to pass into one another, though less defined, possibly inter- 

 mediate forms were seen. In preparations where the blood was 

 at rest, interesting changes of cell-phase were observed ; the first 

 form became spherical, the flagellum grew enormously at the expense 

 of the membrane, and was finally broken off, leaving an amoeboid 

 mass, which occasionally formed long pseudopodia. (There was thus 

 a passage from the ciliated to the amoeboid phase of the " cell-cycle " 

 emphasized by Geddes.) In similar circumstances the third form 

 was observed to retract membrane and flagellum, and to exhibit 

 nuclear division resulting in the formation of a mass of (sixty-four) 

 spores. These became modified into monad-like forms, gradually 

 differentiating, and exhibiting longitudinal fission. A transverse 

 direct division of the first form is also described, and Prof. Danilewsky 

 also observed the formation of buds, without, however, being able to 

 follow out their history. 



Trypanosoma piscium is much smaller and rarer than that of the 

 frog, &c, and occurs in two distinct forms : (a) simple, narrow, and 

 thread-like, with no undulating membrane distinct from the body, and 

 exhibiting extraordinarily lively movements ; (b) spindle-shaped, 

 consisting of a more or less stiff body and a relatively narrow mem- 

 brane, spirally twisted from one end to the other and continued 

 directly into the undulating flagellum. 



Prof. Danilewsky notes the highly developed plasticity of these 

 Hsematozoa, especially of the fourth variety of T. sanguinis, which in 



