FISHERIES, GAME AND FORESTS. 1 87 



this union penetrates an epithelial cell of the gut where it forms spores. These 

 spores migrate into the body cavity of the insect, ultimately finding their way into the 

 salivary glands, and are injected into the blood of a new human host when the pro- 

 boscis of the mosquito is forced into the flesh. Here is a change of hosts which are 

 widely separated in the animal scale, one a warm-blooded vertebrate, the other an 

 inferior invertebrate with body fluids of an entirely different nature. 



A similar change of hosts may occur in other forms of Sporozoa as well as in the 

 malaria germ, and although I do not want, to insist upon it, it is certainly possible that 

 the parasite which is causing the present epidemic is only one phase of some organism 

 which is parasitic in some other form of animal life as well. What that form may be 

 I have no means of knowing. The most probable hosts would be looked for among 

 the arthropods such as flies, small Crustacea, water beetles, and larvae of various kinds 

 or worms of various sorts. The arthropods are the most widely distributed hosts of 

 Sporozoa while worms are almost equally affected. 



On the other hand it may be possible that the form under consideration is a per- 

 manent parasite of the fish, becoming pathogenic only when the means of resistance 

 of its host are weakened enough to permit it to increase to large numbers. Pfeiffer* 

 regards this as a possible explanation of the epidemics among the barbels from the 

 Rhine, Moselle and Saale, which are caused by the allied forms of Sporozoa, the 

 Myxosporidia. I was unable to find them, however, in a presumably healthy fish 

 from another part of the State and regard this view as improbable, although I am not 

 prepared to say that they are not present in healthy fish in Long Island waters. The 

 presence of the parasite in the intestine of the trout indicates that this is the means of 

 infection from host to host, rather than through the gills where I found none, or 

 directly from the outside through the skin. The vital question is : What is the 

 original source of infection ? This question, I regret to say, cannot be answered at 

 the present time. The organism is newly discovered and its affinities are very 

 uncertain. The nearest approach to it are the forms described by Pfeifferf as Sero- 

 sporidia. These are minute parasites occupying the body cavities of various Crustacea 

 {Daphnia, Gammarus, Cypris, several species). Their form is spherical, oval or 

 pyriform, and from four to ninety microns in diameter. The protoplasmic body is 

 finely granular. Reproduction takes place in two ways : either the parasite changes 

 into a cyst the contents of which break up into numerous amoeboid spores, or it 

 divides. The method of infection and the general distribution of these forms are 

 quite unknown. The full life history of these Crustacean parasites is also unknown. 

 It may be pointed out, however, that the hosts in which these parasites live are minute 



* Protozoen als Krankheitserreger. Edition 1891. 

 f Sporozoen als Krankheitserreger. Edition 1895. 



