218 THE HAEMOFLAGELLATES 



may be continued into the posterior flagellum, which then acts as a 

 pulsellum; Leger thinks, however, that this flagellum. functions 

 chiefly as a rudder (Schleppgeissel). The anterior flagellum is not 

 greatly, if at all, concerned in the movement. 



All Trypanosomes undergo, more or less continually, a vibratile 

 or undulatory motion of the membrane, which may take place in 

 either direction. Among the elongated Piscine forms, movements 

 of contortion are much in evidence, the body being frequently 

 coiled up on itself. In many Trypanosomes, again, especially the 

 more spirochaetiform ones, the membrane appears spirally wound 

 round the body, this being due to a more or less pronounced 

 torsion of the latter, which gives the animals a corkscrew-like motion. 



B. Agglomeration. This characteristic phenomenon of Trypano- 

 somes occurs chiefly or only upon the advent of unfavourable 

 biological conditions in the surrounding medium. In the normal 

 blood or other humour of Vertebrate hosts agglomeration has only, 

 been observed in one or two cases, when it has been termed auto- 

 agglomeration. Agglomeration is readily brought about artificially 

 in various ways ; e.g. when drawn blood containing the parasites is 

 kept for some time at a low temperature ; when sera of other 

 animals, especially of animals which have been once or twice inocu- 

 lated with the particular Trypanosome, are added to fresh blood ; 

 or by the addition of chemical solutions. 1 



Agglomeration generally commences by two Trypanosomes 

 coming together and joining (Fig. 14, A) ; and the union may some- 

 times remain only binary. In most cases, however, the agglomera- 

 tion progresses rapidly, a number of parasites collecting round a 

 common centre and forming a multiple union or rosette (Figs. 13 ; 

 14, B). Such a cluster or rosette is known as a primary agglomera- 

 tion, and may consist of as many as a hundred individuals ; some- 

 times the rosettes themselves become grouped together to form large 

 tangled masses. In a natural (as opposed to an artificial) medium, 

 agglomeration of a particular form of Trypanosome takes place, 

 typically, by the same extremity. In Trypanomorpha noctuae, accord- 

 ing to Schaudinn, this is the flagellate (anterior) end; i.e. the 

 parasites unite with the flagella pointing towards the centre (Fig. 13). 

 In Trypanosoma^ on the other hand, the union is by means of the 

 aflagellar end. 2 



1 For fuller details the reader is referred to the works of Laveran and Mesnil 

 (37, 43), Lignieres (54), Thiroux (83), and others. 



2 In artificial cultures, clusters are frequently observed in which the arrangement 

 of the parasites is not constant, even in the same species ; that is to say, some- 

 times the Trypanosomes have their flagella at the periphery, while at others the 

 flagella are centrally directed. It appears, however, that two entirely different pro- 

 cesses are concerned. In some cases, at any rate, those clusters which have the 

 flagella pointing centrally are instances not of agglomeration, but of rapid successive 

 division, where the parasites remain more or less in contact and form large colonies. 

 This has been well Brought out by Novy and M'Neal (62. 63), Thiroux, and others. 



