EMBRYOS OF THE TJENIAD.E. 323 



Besides the shelled embryo, this generally encloses a number of 

 shining fatty granules which are often collected in large clusters. In 

 older eggs, this albuminous layer is often completely lost, so that the 

 thick shell is then the only embryonal envelope. 



The difference between these embryo-containing eggs and the 

 original contents of the uterus is so striking, that it is right to in- 

 quire into the processes by which the latter are transformed into the 

 former. This investigation is, however, anything but easy, especially 

 in the large-hooked Tcenice, whose eggs can be isolated only with 

 difficulty. On the strength of my later observations, I am obliged to 

 modify in many ways the statements which I formerly made re- 

 garding the embryonic development of the Tcenice, which were, how- 

 ever, the first published. 1 



I recall, in the first place, that the eggs on which our description 

 is to be based are not simple ovarian eggs, but consist of these, plus an 

 albuminous enveloping substance, which is covered exteriorly by a thin 

 and transparent skin the primitive shell-membrane. The whole struc- 

 ture has the appearance of a more or less spherical ball of about 0'03 

 mm., which at first sight one might easily take for a simple cell with 

 a large vesicular nucleus (0*018 mm.). Only gradually does one per- 

 ceive that the nucleus is surrounded by a narrow, membraiieless coat- 

 ing of protoplasm, which, with its contents, is really the ovarian egg. 

 Besides the latter, the enveloping substance in T. solium and its re- 

 latives generally contains one or two shining fatty bodies of varying 

 size (up to 0*01 mm.), and of a usually homogeneous but sometimes 

 granular nature. Sommer, who describes the bodies as accessory 

 yolk-granules, thinks that they originate directly in the ovary ; and 

 it is true one sometimes finds in it granules similar to, though hardly 

 identical with, those occurring in the protoplasmic envelope. 



As everywhere, the embryonic development of the Tcenice is 

 effected by a division of cells, by a process which seems to associate 

 itself primarily with the persistent and apparently unaltered germinal 

 vesicles. But on account of the small size of the developing mass, and 

 the clear nature of the enveloping protoplasm, this division assumes, 

 especially at first, a very unusual appearance, which easily leads to a 

 wrong conception of it, and which indeed, so long as I was ignorant 

 of the yolk-coating of the ovarian egg, led me to imagine a formation 

 of daughter-cells in the interior of the germinal vesicle. On the whole, 



1 " Blasenbandwiirmer," p. 14, and the first German edition of this work, Bd. i., p. 

 184. See also the descriptions of the younger van Beneden in his " Recherches sur la 

 composition et la signification de 1'ceuf," p. 51 : Brussels, 1870 (Mem. couronn. Acad. 

 Bdg., 1868) ; as also Moniez, Comptes rendus, Nov. 1877, and Bull. sci. dep. du Nord., 

 t.x., p. 227, 1879. 



