1 86 REPORT OF THE COMMISSIONERS OF 



ectoplasmic, and a denser endoplasmic region, the spores being in the latter (Figure 

 7, E). A more or less definite membrane separates the two regions. This membrane 

 is not obligatory, however, and is often wanting. 



The spores thus formed are liberated into the body cavity and are carried to all 

 parts of the body with the lymph and blood. Whether they are voided to the outside 

 or not, I do not know. In some cases the cysts, which are most often found in the 

 body cavity, were observed in the intestine and I can account for their presence here 

 on the assumption that they had been taken in as food or else derived from the gall 

 bladder, for in no case have I found amoeboid stages in the digestive tract. If they 

 are voided to the outside it is probably by way of the gall bladder, for in this organ 

 they were very abundant. 



Briefly summarizing the above observations it appears that the parasites are 

 i) taken into the digestive tract with the food either in the cyst (adult) stage or in the 

 spore stage; 2) the spores form sporozoites in the stomach and intestine; 3) these 

 penetrate the epithelial cells and work their way to the lymph spaces ; 4) in the lymph 

 they develop amoeboid processes and then penetrate muscle bundles; 5) here they 

 grow to the adult stage, becoming comparatively large amoeboid organisms of spindle 

 or club shape; 6) they return to the lymph and there round out into spore-forming 

 cysts ; 7) the spores are apparently formed by the segregation of chromatin (?) granules 

 which leave the remaining protoplasm with a distinctly reticular structure ; they are 

 variable in number ; 8) the spores are liberated in the body cavity from which they 

 find their way to all parts of the body, but accumulate especially in the testis. Or 

 the cysts may be voided to the outside by way of the gall bladder ; 9) in the testis 

 these spores form sporozoites and thus lead to auto-infection. These spores, unlike 

 those in the intestine, are covered by a capsule. 



I am not satisfied to conclude, however, that the entire life history of the parasite 

 is to be found in the trout. The absence of all traces of conjugation leads me to 

 believe that some important stages in the life history are passed in some hosts other 

 than this fish. I may digress from my immediate subject long enough to point out a 

 case which illustrates this point and which has only recently been made known 

 through researches of Major Ross in India, of Professors Koch, Grassi and others in 

 Germany and Italy. The malaria-causing organism in man {Plasmodium malaria;) is 

 a parasite belonging to the same group (Sporozoa) as the fish parasite here considered. 

 Its life history was not completely known until within the last two years, when it was 

 discovered that a very important stage in its development is passed in the digestive 

 tract of a mosquito. Professor Koch and other scientists in Germany found that the 

 malaria germs which are taken with the blood into a mosquito's stomach, conjugate 

 there in pairs, a male germ fusing with a female. The copula which is formed by 



