THE AMERICAN NATURALIST [Vol. XLII 



Trypanosomes. — The life history of various trypanosomes has 

 been investigated with great care at the Runcorn Research Labo- 

 ratory, Liverpool, by J. E. S. Moore and A. Breinl, with several 

 collaborators. The results appear to be uniform and to differ 

 markedly from those of previous work. These authors are un- 

 able to make any distinction between the so-called male, female 

 and parthenogenetic forms of Schaudinn and hold that mere 

 varieties in size or even in some morphological features when 

 taken from different parts of the life cycle should not be spoken 

 of under terms which imply conjugation when no such phe- 

 nomenon takes place so far as is known. Trypanosoma gambiensc 

 and T. lewisi manifest a cyclical metamorphosis corresponding 

 closely to alternate presence and absence of the parasites from 

 the blood. Periods of maxima and minima alternate irregularly 

 and not with the definite chronicity seen in the development of 

 the malarial organisms. The coming of a minimum is accom- 

 panied by the formation of latent bodies consisting of nucleus 

 and vesicle enclosed by a delicate covering of cytoplasm. These 

 latent bodies lodge chiefly in the spleen and bone marrow and 

 from them are developed later a new generation of the typical 

 flagellate forms. Associated with the formation of the latent 

 bodies is an interaction, which occurs at or near the maxima, 

 between the extra-nuclear centrosome, perhaps better named 

 the blepharoplast and the nucleus. It is inferred that the real 

 sexual phase occurs within the transmitting insect, although 

 other investigators look upon the role of the latter as purely 

 mechanical. 



In T. equiperdum, which is the cause of dourine, the entire 

 life history is confined to a single animal and not complicated by 

 transfer through an intermediate host. When inoculated in a 

 rat the process appears identical with that outlined above, save 

 that the round forms which occur at the period characteristic 

 of latent bodies possess two long and delicate flagella. There is 

 in the rat but a single maximum which is followed by the death 

 of the host ; in horses the parasites are not sufficiently numerous 

 to permit the observer to follow the changes which take place. 



H. B. W. 



