ZOOLOGY AND BOTANY, MICROSCOPY, ETC. 647 



Parasites of Fresh-water Fishes.*— M. F. Zscbokke has been in- 

 vestigating the organization and zoological distribution of the para- 

 sitic worms of fresh-water fishes. He has examined twelve species 

 from the Lake of Geneva, among which are Perca fluviatilis, Cyprinus 

 carpio, Trutta variahilis, Salmo umbla, and Esox luciiis. The first 

 result of these studies is to demonstrate the presence of 37 species 

 of parasitic worms ; three at least of these are new species ; they are 

 found in nearly all the organs of the body ; six of the eleven species 

 of Cestoda were found in the strobila-stage, two in the scolex, and 

 three in both. Only three of the species had no special parasite 

 (namely, Coregoniis, Trutta, and Ctjprinns carpio). A table of distri- 

 bution shows that the rapacious fishes (Salmonidse, Gadidse, Esocidee) 

 are the richest in different species of parasites. The genera of 

 parasites have a close relation to the food of their host ; thus the 

 carnivorous forms have a very remarkable preponderance of adult 

 Cestoids ; on the other band, the Ctjprinidce, which are herbivorous, 

 are rich in Acanthocephali, for with their vegetable nutriment they 

 take in a number of small Crustacea. The Trematoda are very 

 regularly distributed ; Nematoids are found in nearly all. 



The author further directed particular attention to the difficult 

 question of whether the parasites are the same throughout the year, 

 or vary with different seasons, and, so far as he was able to judge, 

 he found that the number of parasites does not vary considerably 

 daring the year. He notes, lastly, what must have struck other ob- 

 servers, that the number of female Ascarids is excessively large in 

 proportion to the males. 



The i)receding introduction to the paper is amply supplied with 

 very valuable tables of statistics. 



Dealing with the species in detail, the author gives notes on the 

 various forms : Taenia salmonis umhlce is a new species found in the 

 intestines of Salmo umhla ; it is from three to five centimetres long, 

 the jointing is only feebly indicated, and the head has, on its anterior 

 surface, a slight depression, which has the appearance of being a 

 large but very shallow sucker. The genital orifices are placed in 

 pits, and alternately, though not regularly, on either side. No ripe 

 proglottids were detected. The author j^roposes to unite the species 

 distinguished by Eudolphi as Bothrioceplialus infundibuliformis and 

 J5. j/roboscideus. 



Nothing is to be added to the excellent account given by Pintner 

 of the excretory system of Tricenophorus. 



Distoma nodulosum was found in eight of the twelve hosts ex- 

 amined, and D. glcMporum is very widely distributed ; D. tereticolle 

 is most common in the trout. With some hesitation, Biphzoon 

 paradoxum, in its Diporpa-atagc, is reported from the gills of Lota 

 ruk/aris and Cottus gohio. 



Sporoajstis colli n. sp. was very frequently found in the muscles 

 of Cottus gohio, under the form of small, whitish, elongated cysts, but 

 the Dietomum to which they belong has not yet been discovered. 



* Arch, de Biol., v. (1884) pp- 153 241 (2 pis.). 



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