180 BULLETIN OF THE UNITED STATES FISH COMMISSION. 



Section IV. die langcyliudrische sog. Ilolophrya oblonga Maupas mit feiu zertheiltera Nucleus, 

 die wahrsrheiulich ideutisck mit der sog. H. marina Daday's (Makronucleus rosenkranzformig) ist and 

 welcherauch wohl der Proration marinus (Clap. u. L. 301, sowie Queunerstedt 408b und Miibius 18881 

 nabe steht. Letztgeuanute Formeu besitzen jedocb auch wohl Beziehuugen zu Chaenia Quenuerst. 



Weissinann (L891) makes a passing reference to Fouquet's species as "an exam- 

 ple of the phyletic origin of germs among the lower flagellata and gregarines." 



Zacharias (1892a and 1892ft) found an Ichthyophthirius on Leuciscus rutilus and 

 Alburnus sp. kept in a large aquarium in the biological station in Plon. The para- 

 sites formed pustules in the skin of their hosts, and were situated especially on the head 

 and along the lateral lines; in some cases the fish were practically covered with them. 

 The ciliates measured 0*65 to 80 mm long by 0-50 to 0*55 mm broad ; the dorsal surface 

 is described as convex, the ventral surface as flat, and the entire body is covered 

 with short (5,u) cilia; the protozoan possesses a large horse-shoe shaped nucleus, which 

 is situated in the pointed anterior half of the body. By direct light the animal 

 appears white ; by transmitted light, grayish yellow. The anterior end is somewhat 

 lighter in color than the middle and posterior portion, due to the uneven distribution 

 of granules and crystals in the endoplasm. The endoplasin has a vacuolated struc- 

 ture and contains in the plasma between the vacuoles numerous round and angular 

 refringent bodies. Besides these are found collections of dark granules (= pigment of 

 other authors) probably to be looked upon as metabolic products. The thickest portion 

 of the nucleus is at the bend and measures 0*05 mm. Like Fouquet, Zacharias 

 believes that although the nucleolus is present in the young it is absent in the adult. 



Zacharias states that no mouth is present, but on the ventral surface he found 

 a depression 0-035 mm deep, 0-015 mm in diameter, which he interprets as a sucker 

 by means of which the young fasten themselves to their host. He found no portions 

 of food in the endoplasm, and experiments to feed powdered carmine were negative, 

 from which Zacharias assumes that the parasites feed in some way upon the body fluids 

 of their hosts. Contractile vacuoles were absent. As Fonquet's species presented 

 a terminal anterior "mouth," and as this organ in Zacharias's species is situated 

 ventrally in the anterior third, Zacharias looks upon it as a new species, for which 

 he proposes the name I. cryptostomus. 



Zacharias believes that the parasite which he observed is identical with the form 

 found by Hilgeudorf and Paulicki, basing this opinion on the statements of Hilgen- 

 dorf and Paulicki that in their form the "mouth" was absent, while Zacharias doubts 

 whether it could have been easily overlooked had it been terminal, as in the case of J. 

 multijiliis. Furthermore, Hilgeudorf and Paulicki state that the encysted parasite 

 segmented into 100 to 150 young, this agreeing with the form examined by Zacharias, 

 while Fouquet's species segmented into nearly 1,000. 



Regarding the reproduction, Zacharias states that the ciliates which have left 

 the fish lose their cilia and form a cyst around themselves, which he looks upon as the 

 thrown-off cuticle, the content dividing until the young cells measure 0-075 mm in 

 diameter. The macronucleus of the young measures 0-025 mm, the micronucleus 

 0-004 mm, and the cilia of the young are about twice as long as the cilia of the adult. 

 As the young globular animals become oval or ovoid the globular nucleus elongates 

 and becomes crescentic. While former authors had not found any stages of repro- 

 duction while the parasites were still on the fish, Zacharias states that he frequently 



