714 OCCURRENCE AND DEVELOPMENT OF BOTIIRIOCEPHALUS LATUS. 



malformation, so far as my researches go, by the interpolation of a 

 half (sometimes only imperfectly separated) joint. This is again re- 

 peated, as the adjoining figure shows. The second half joint, of course, 

 belongs to the opposite side. 



Occurrence, and Development of Bothriocephalus latus. 



Knoch, " Die Naturgeschichte d. breiten Bandwurmes mit besond. Beriicksichtigung 

 seiner EntwickelungPgeschichte. " M6m. Acad. Sci. St. Petersb., t. v., 1862. 



Knoch, "Neue Beitrage zur Embryologie dea Bothriocephalus latus." Bull. Acad. 

 imptr. St. Petersb., t. xiv., p. 178, 1869. 



Leuckart, " Die menschlichen Parasiten," 1 eA, Bd. i. f p. 757, Bd. ii., p. 867, 1863. 



Bertolus, "Sur le developpement du Bothrioce'phale de rhomme." Comptes rendus, 

 t. Ivii., p. 569, 1863. 



Braun, " Zur Entwickelungeschichte des breiten Bandwurmes : " Wiirzburg, 1883. 



Schauinsland, " Die embryonale Entwicklung der Bothriocephalen.' Jenaische 

 Zeitschr.f. Natunoiu., Bd. xix., 1885. 



The problem of the occurrence and development of Bothriocephalus 

 latus has only received satisfactory solution during the last few years. 

 Since this tape-worm is found especially in districts where water is 

 very abundant, and since the nearest relations of this worm are found 

 mostly in aquatic animals, the opinion has been for long expressed 

 that the intermediate host of this parasite was some aquatic animal, 

 which transmitted it in its young stage to man. Fishes were first 

 thought of, and it was sometimes supposed that the delicate trout and 

 salmon were the hidden homes of the Bothriocephalus embryos. 



The probability was increased, when Schubart of Utrecht, accord- 

 ing to a communication of Kolliker's, 1 developed the ova of this tape- 

 worm in water, and observed the liberated embryo with its mantle of 

 cilia. Schubart's observations were unfortunately not published in 

 detail. 2 They would perhaps have been forgotten, had not similar 

 investigations, twelve years later, pursued contemporaneously in 

 Eussia, France, and Germany, by Knoch, Bertolus, and myself, led 

 essentially to the same results. All agreed that the development of 

 the embryo occupied usually several months, varying with external 

 conditions, and especially with the temperature. The liberation only 

 occurs during the warm season, so that ova formed in September are 

 not liberated till April of the next year. Except in the ciliated 

 envelope, which surrounds them at some distance, the embryos essen- 

 tially resemble the long-known embryos of Tcenice, especially in 

 bearing the characteristic hook-apparatus. 



1 Zeitschr. f. wiss. Zool., Bd. iil, p. 86, 1851. 



2 The reports which Verloren gave at the Assembly of Naturalists at Bonn (Tage- 

 blatt, p. 19, 1855) as to the observations of his deceased friend, do not really extend the 

 communications of Kolliker except in expressly tracing the ciliated embryos to Bothrio- 

 cephalus latus. 



