Miscellaneous. 149 



with the establishment in Egypt of the family of Jacob, in the time 

 of the later Shepherd Kings. This mention of the horse nearly co- 

 incides, in point of time, with the most ancient notice of that 

 animal on Egyptian monuments. The author thinks it possible that 

 the introduction of the horse into Syria and Egypt was effected by 

 the invaders from whom the Shepherd Kings were derived. — 

 Comptes Rendus, tome Ixix. December 13, 1869, pp. 1256-1258. 



Embryonic Development of Bothriocephalus proboscideus. 

 By E. Mecznikow. 



M. Kolliker has already remarked that in Bothriocephahis pro- 

 boscideus only a part of the contents of the ovum is employed in the 

 formation of the embryo, and that the rest forms a layer of peri- 

 pheral cells, the fate of which remained unknown to him. M. Knoch 

 disputed the accuracy of this observation, but wrongly, as it now 

 appears. M. Mecznikow describes the ova of this Cestoid worm as 

 filled by an ovarian cell surrounded by a mass of granular vitellus. 

 The cell undergoes total segmentation, whilst the vitelline mass 

 takes no part in the formation of the embryo. Erom the cellular 

 aggregation produced by segmentation, two cells, furnished with 

 larger nuclei than the others, are soon seen to separate ; they fix 

 themselves at the two poles of the ovum, and only disappear at the 

 close of the embryonic life. M. Mecznikow has seen [a perfectly 

 similar arrangement in the ova of Tcenia cucumerina. 



After the segmentation, the mass of embryonal cells acquires a 

 rounded form, and the embryo divides into a central nucleus and a 

 peripheral layer, the latter formed of very distinct cells. ^Tiilst the 

 nucleus forms the true larva of the Cestoid worm, with its booklets, 

 the layer of peripheral cells becomes converted into a delicate mem- 

 brane, which finally loses its cellular structure and acquires the 

 appearance of a homogeneous cuticular envelope. 



Although this envelope of the embryo never becomes covered with 

 vibratilc ciHa, M. Mecznikow does not hesitate to compare it to 

 the ciliated envelope of Bothriocep]ial.as latiis. In fact, the embryonic 

 development of B. proboscideus shows that the embryonal envelope 

 is the homologue of the amnios of the embryos of Insects and other 

 Arthropoda. In this case the ciliated envelope of the larva of B. 

 latus would be a sort of amnios persisting for a long time after 

 hatching. But then we must extend this homology to the ciliated 

 embryos of the Monostoma and of M. Desor's Nemertean. To be 

 consistent, we must even regard Pdidium as a sort of temporary 

 envelope of its Nemertes, as an amnios which has attained a remark- 

 able degree of independence. — 3Ielanr/es Biologiques tires du Bulletin 

 de VAcad. Imp. de St. Petersb. tome vi. p. 717 ; Bibl. Univ. January 

 15, 1870, Bidl. Sci. p. 87. 



Ifote on a Station of a living Encrinus (Pentacrinus europaeus) iipon 

 the Coasts of France. By M. Lacaze-Dtjthiers. 



Since the investigations of Messrs. W. Thomson and Carpenter, 



