INTRODUCTION. 



These are a few of the notices we have hap 

 pened to meet concerning the exhihition of this 

 extraordinary disease in fishes. They are interest- 

 ing, not only as opening up a new field of research, 

 but also as bearing upon the Natural History of the 

 class ; and not less so, as the phenomena of the 

 complaint in these animals may possibly elucidate 

 the occurrence of the disease in higher classes, and 



times in the Perca fluviatilis. In conclusion, the Professor 

 states, " That there was here a disease of the skin and internal 

 parts, produced by a kind of seminal corpuscule, which had no 

 relation to animals which are propagated by means of a semini- 

 /jrous ova, nor with the Entozoaires, or tailed Cercaires, nor were 

 they less distinguished, by their structure of hair-like parasite 

 formations, from animal organisms ; and, finally, widely different, 

 by their specific character, from all known cellular formations, 

 whether normal or pathological." In the latter, entitled Obser- 

 vations upon the Psorospermies, the author enumerates a great 

 number of fishes, European and Foreign, in which he had in 

 vain searched for this disease, and a few in which he had found 

 it.. The disease which had been noticed in the German perch, 

 was also found in perches brought from the rivers which empty 

 themselves into the Arctic Sea, by MM. Humboldt, Ehrenberg, 

 and Rose ; and, finally, he states, " That these parasites, which 

 have been observed in the fresh-water fishes of Europe, Asia, 

 Africa, and America, and which consist of the two principal 

 forms above alluded to, those with tails and those without 

 them, are absolutely the same in every region of the globe. 

 They evidently possess a life which is peculiar ; but they have 

 no power of movement, or, rather, they are organic beings, 

 like plants, possessing a structure perfectly distinct from the 

 cellules, healthy or diseased, of animal tissue ; having no re- 

 semblance to the kind of warts which many Naturalists have 

 noticed in some kinds of fishes/* 



