Miscellaneous. 473 



On the Bevelopment of the Bothriocephalus latus. 

 By M. Bertolus. 



The egg of the Bothriocephalus requires for its complete develop- 

 ment a residence of from six to eight months in running water or 

 water frequently renewed. At the moment of the rupture of the 

 ovisac, the egg is composed of a dark brown, resistant, ovoid shell, 

 exactly filled with an amorphous granular mass. "Within a month 

 this vitellus divides into cells of 0*015 millim. in diameter ; soon after- 

 wards a transparent spot (embryonal spot) makes its appearance in 

 the centre, and is slowly developed at the expense of the vitellus, the 

 latter at the same time contracting, so as to leave a space between it 

 and the capsule. 



In six months the embryonal spot has invaded the whole vitelline 

 mass ; at this time the embryonic booklets make their appearance, 

 and the embryo already manifests some movements of contraction. 

 Lastly, at the end of seven or eight months a sort of operculum 

 separates from the small extremity of the capsule, and furnishes a 

 passage for the embryo. 



The embryo consists of two spherical bodies, one within the other. 

 The external' body has the form of a hollow sphere 0'04.5-0*05 mil- 

 lim. in diameter; its wall is about 0*01 millim. in thickness, formed 

 of large prismatic cells pressed against each other, and clothed ex- 

 ternally with a quantity of large vibratile flagella of extreme tenuity, 

 very flexible, and O'0 10-0*0 15 milUm. in length. By the impulsion 

 of this vibratile apparatus the whole embryonal mass swims rapidly at 

 the moment of its exclusion, turning upon itself ; but in a few hours 

 the movement slackens, ceases soon afterwards, and the ciliary coat 

 seems to disappear. 



Within this hollow sphere is another body, likewise of a spheroidal 

 form, moving freely in its envelope, and armed towards one of its 

 poles with three pairs of booklets perfectly analogous to the six 

 booklets characteristic of the embryos of Taenia. This inner body, 

 formed of very pale nucleated cells (0*005 by 0*003 millim.) measures 

 from 0*035-0*04 millim. in diameter. 



The booklets, which are apparently similar in the three pairs, at- 

 tain a total length of 0*013 millim. ; the blade, which is but slightly 

 curved, is about one-third of the total length ; the haft, which is 

 straight and very slender, is 0*009 millim. in length ; the dental 

 process projects considerably (0*0028 millim.). 



The analogy presented by this embryo on the one hand with 

 the embryos of the digenetic Trematoda, and on the other with 

 those of the Ttenice, seems to indicate clearly that this young parasite 

 is destined to become encysted in the parenchyma of some aquatic 

 animal for its further development. 



In connexion with the latter, the author calls the attention of 

 zoologists to a parasitic worm which he considers will prove to be 

 the scolex of the Bothi'iocephalus latus. This is the Ligula nodosa 

 of Rudolphi, which lives encysted in the conjunctive tissue of various 

 species of the genus Salmo, with regard to which he states that he 

 has ascertained it to be a scolex, of which the so-called cephalic 



Ann. ^ Mag. N. Hist. Ser. 3. Vol. xii. 81 



