REPORT UPON A PARASITIC PROTOZOAN. 177 



Thus, as we shall see, the first observers, although they did not go iuto minute 

 details in regard to the microscopic structure of the parasite, made very exact obser- 

 vations 011 its life-history, and all the work on this form which has been done since 

 then confirms most of their observations, corrects some slight errors, and supplements 

 their description by furnishing details which escaped their notice. 



Fouquet (1876) found numerous nearly spherical parasites, 0-3 mm to 0*8 mm in 

 diameter, on small trout in Prof. Balbiani's laboratory (College de France, Paris), 

 which he identified as the form found by Hilgendorf and Paulicki. They rotated, 

 according to his observations, from left to right as well as from right to left in a cyst 

 formed at the expense of the epithelium; the cilia were arranged regularly in rows as 

 already noticed by Hilgendorf and Paulicki. In the cortical layer of the ciliate were 

 found trichocysts and numerous contractile vacuoles, 0-03 mm in diameter. The endo- 

 plasm contained granules which carmine would not color and which were insoluble in 

 caustic potash and only slightly soluble in ether and alcohol. 



The larger specimens contained irregular patches of blackish pigment. The 

 mouth was on the anterior extremity, non-contractile, 0-04 mm in diameter and 

 surrounded by cilia which are slightly longer than those of the body; an oesoph- 

 agus was present. Fouquet does not believe that this orifice can be used as a mouth, 

 but rather that it serves as a sucker, while the parasite' absorbs its nourishment by 

 endosniosis. The nucleus is described as horseshoe-shaped, 0-30 mmlongby 0-09 mm 

 broad; the nucleolus could not be discovered in the adult, but was found in the 

 young. When the parasite has reached a certain stage, it leaves the fish, falls 

 to the bottom of the aquarium, forms a cyst around itself and divides in the series 

 2, 4, 8, 1C, etc., until about 1,000 small cells are formed. The division is completed 

 in about 40 to 50 hours, the time varying according to the temperature. On the 

 third or fourth day the young, which measure 0-046 mm by 0*028 mm, escape from 

 the cyst and seek new hosts. The trichocysts are more visible in the young than in 

 the adulf. The nucleus is 0-015 mm in diameter and in part incases the nucleolus, 

 but each has its own membrane. The nucleolus measures 3-1 jj in diameter. Fouquet's 

 attempt to infect fish with the young parasites gave negative results. The epizootic 

 began each year towards the end of May, and lasted two or three months. While 

 Hilgendorf and Paulicki considered this parasite related to Pantotricha Ehrbrg., Fou- 

 quet considers it a representative of a new genus of Heterotricha, for which he proposes 

 the name Iehthyophthirius (I. multifiliis). 



erne weitgebende Tbeilung nach vorberiger Encystirungbeobacbtet werden, wiibrend die unmittelbar 

 voni Fiscbe berabgeiioinmenen Individuen nie die Andeutung eines Tbeiluugsprocesses erkennen 

 liessen. Tbeiltbiercben wurden in verscbiedenen Beobacbtimgen. 2, 4, 8, 16 bis zu etwa 100 und 

 dariiber gezablt. Wurde die geineinschaftlicbe Hiille durch Druck zuin Bersten gebracbt, so driingten 

 sich die kleinen Nacbkoimnen des Muttertbieres bervor mid scbwammen in schneller Bewegung als 

 anfanglicb ovale, rotirende Gebilde lebbaft umber. 



Wabrscbeiiilicb werden diese kleinen Tbeilsprosslinge wiederuin einen Fiscb aufsucben, urn an 

 ibm durcb reicblicbe Nabrung Wacbstuni und abermalige Tbeilungsfabigkeit zu erwerbeu, und uni 

 danu denselben, soeben dargestellten Kreislauf der Entwicklung zu wiederbolen. 



Die Fiscbe selbst mussen natiiiiicb, zumal durcb massenbaftes Auftreten dieser Schniarotzerforni 



bedeutend leiden, in dein sicb die Oberbaut in Fetzen ablost und die Function der Haut wesentlicbe 



Beeintriicbtigung erfabrt. Die Pilzbildung scbeint erst auf dem abgestossenen Epitbel als secun- 



diirer Process vor sicb zu geben, und darf somit wobl nicbtalsein wesentlicbes Moment der Krankbeit 



angeseben werden. 



F. C. B. 1893—12 



