12 PROTOZOA AND DISEASE 



Having escaped, the gymnospores develop a sheath, protrude lobo- 

 podia, and, the nucleus multiplying by mitosis, the monont thus 

 constituted resembles the amphiont (Fig. 2 ; 4) in all details save the 

 absence of the rods from the sheath. The fully developed mononts 

 or sporonts increase vegetatively by constriction (Fig. 2 ; 4a, 4b), in a 

 way similar to that described for the amphiont, and multiple sub- 

 division in the resting state also occurs, but in a manner different 

 from that described for the amphiont. After food particles have 

 been extruded, the protoplasm becomes vacuolated, and numerous 

 bright protein particles appear. Simultaneously the nuclei sub- 

 divide by mitosis (Fig. 2 ; 6), and the body subdivides into larger, 

 and these, again, into smaller, bodies, which move rapidly about, and 

 on the rupture of the sheath show themselves as swarm-spores, each 

 provided with two flagella (Fig. 2 ; 6). These swarm-spores are sexual 

 cells, or gametes, which appear to be unable to unite with gametes 

 arising from the same sporont as themselves, and hence most of 

 them perish ; but if a brood of gametes that have originated from 

 another sporont is near, the individuals of the two broods pair 

 off, forming zygotes by total fusion, the four flagella having been 

 discarded. This process lasts six hours, and twelve hours later 

 nuclear division and the formation of a sheath are begun. After 

 this the lobopodia appear, and the developmental cycle is completed. 



The temporary association of amoebae or plastogamy has been 

 already referred to in Part I. in the diagram illustrating the average 

 life-cycle in the sarcodina ; the phenomenon is common in the 

 shelled amoebae, such as Arcella and Patella. The fact that there is 

 a sexual phase in the life-cycle of Trickosph&rium points to this 

 character being common to the whole group of protozoa. 



The importance of the sexual process in protozoan disease is 

 very great. From the fact alone that the virus of yellow fever 

 is intensified by its passage through the gnat, Calkins believes 

 that a sexual phase of the, at present, unknown parasite may be 

 inferred. 



Even a cursory study of this amoeba Trichospharium suffices to 

 show how difficult it would be to distinguish a degenerate parasitic 



