300 ILLINOIS ACADEMY OF SCIENCE 



Notropis blennius Homer 



N. gilberti Stony Creek 



Pomoxis annularis Crystal Lake 



Trionyx spinifera Crystal Lake 



As will be seen from the above, tbe myxosporidian in- 

 fection among the common fish in this locality is heavy. 

 Only five out of eighteen species of fish were proved to 

 be free from infection at the time of examination. Yet 

 too much emphasis can not be laid upon the absolute ab- 

 sence of Myxosporidia in these fish, as the number of in- 

 dividuals in each of these five species was not great and 

 besides observations were not made during the summer 

 months. 



The writer could not collect, and study the fish through- 

 out the year. In the fish obtained during colder months, 

 there was strong evidence which suggested that only 

 plasmotomous multiplication of the parasites took place. 

 On the other hand, in the specimens collected in June 

 and July, remarkably rapid growth of parasites due to 

 plasmotomous as well as sporogonic development were 

 clearly noticed. This was well demonstrated in the case 

 of Mitraspora elongata Kudo, parasitic in the kidney of 

 Lepomis cyanellus caught in Crystal Lake. Early in June 

 vegetative forms and spores were seen to be present in 

 the lumen of the urinary tubules of the kidney of host, 

 while in the latter part of June and in July the vegetative 

 forms became considerably larger and larger, and ap- 

 peared as more or less conspicuous cysts in the tissue of 

 the kidney, forming frequently numerous small whitish 

 pustules on the surface of the organ. These observa- 

 tions simply verify similar observations made by sev- 

 eral investigators especially on such a form as Myxobolus 

 pfeifferi Thelohan. 



