76 American Fisheries Society. 



ficial features, would seem to supply the essential conditions 

 for the maintenance of the organism were it indigenous in the 

 trout of the lake. 



The net result in the search for Octomitus among the brook 

 trout of these waters in the hatcheries and in the lakes has 

 been negative. Added to this negative evidence is the positive 

 evidence of our infected hatcheries, where the brook trout are 

 the most susceptible of all trout species, their susceptibility 

 distinctly limiting the period under which they can be carried 

 successfully. This very susceptibility yields strong evidence 

 that the organism is not indigenous when we reason by anal- 

 ogy from the manner in which many of our native plants 

 and animals, unimmunized to the disease germs introduced 

 from abroad, succumb to their ravages. 



The possibilities for determining the indigenous or non- 

 indigenous character of the germ are by no means exhausted 

 and to this extent the problem further presents an interesting 

 subject for speculation. If not indigenous, how did the or- 

 ganism get here? Was it introduced into our brook trout 

 waters by way of the Brown or Loch Leven trout from 

 Europe? The inference is strong that it has been introduced 

 in this manner. 



The history of the organism bears strongly on the point. 

 Last year Dr. Davis, of the U. S. Bureau of Fisheries, and I, 

 working at different hatcheries, simultaneously recognized 

 Octomitus as the infecting organism responsible for epidemics 

 of enteritis at the respective hatcheries under observation. 

 Hitherto this organism had not been observed or described in 

 this country. In Europe, however, this, or a similar organ- 

 ism, has been known for twenty years. In 1903 Moroff de- 

 scribed it as the inciting cause of disease among the introduced 

 rainbows of their hatcheries, and he makes the interesting ob- 

 servation that the browns are less affected. This is just what 

 might be expected to happen to the non-immunized rainbows 

 by contrast with the more hardened native browns. In 1920 

 Schmidt re-described Moroff 's organism, which for nearly 

 twenty years had been masquerading under the name of 

 Urophagus intestinalis, and rechristened it Octomitus intest- 

 :>ualis truttae. I have strong suspicions that this and our own 

 species, Octomitus salmonis are identical, and that our species 

 was introduced and has now become a naturalized citizen. 



The infection by Octomitus of wild waters flowing from 

 hatcheries in which octomitiasis exists seems inevitable under 

 the circumstances, for infectious material is constantly being 

 discharged by diseased fish into the waste waters which enter 

 the streams. As is usual in such streams there are numerous 

 fish which come up to the hatchery outfalls for stray morsels 



