42 M. Oscar von Grimm on the Agamic Reproduction 



developed are furthest from the terminal filament, and when 

 they have attained a certain degree of maturity they fall 

 apart like the proglottides of the Tapeworm. 



The development of the ova, like that of cells, takes place 

 by endogenous division. Each ovarian tube represents an 

 elongated cell, as we have already seen ; in this cell or 

 tube the terminal portion of the contents with the half of the 

 nucleus becomes constricted off (fig. 11), the nucleolar cor- 

 puscle having been previously divided *. A cell thus cut off 

 is the germ-chamber, which, after the deposition of the vitellus, 

 becomes directly and completely converted into the ovum ; 

 and that portion of the ovarian tube from which the germ- 

 chamber has been constricted off may be designated the vitel- 

 line chamber or terminal chamber f, so long as it has not yet 

 given off the following germ-chamber. Then commences the 

 constriction of the second or younger germ-chamber, and 

 afterwards that of the third, and so on. The contents of the 

 separated cells or germ-chambers, the future ova, consist of 

 large round vitelligenous cells J (Stein). These vitelligenous 

 cells extrude oil-drops, and at the same time become converted 

 into the vitellus of the futm-e ovum. The vitellus therefore 

 originates from the same elements which have also formed the 

 epithelial cells of the ovarian tube§. As the mass of the 



* From this it is clear that the nucleolar corpuscle by no means plays 

 so unimportant a part as Leuckart, for instance, supposes (art. " Zeugung," 

 Wagner's Handworterb. der Phys. Th. 4. p. 815) ; on the contrary, the 

 nucleolar corpuscle appears, so to speak, to give the impulse of the divi- 

 sion, superinduces the division of the nucleus, and therefore also the 

 development of the germ-chamber corresponding to the ovum. But the 

 nucleus appears to e-xert no such essential influence upon the division ; 

 for whilst it divides after the commencement of the constriction of the 

 protoplasm, its function only commences subsequently. Lubbock says 

 that the nucleolar corpuscle is only subsequently developed (see note 

 infra, §). 



t Claus, " Beobacht. iiber die Bildung des Insecteneies," Zeitschr. fiir 

 wiss. Zool. Bd. xiv. p. 43. 



X Meyer calls the vitelligenous cells abortive ova, and to their nuclei, 

 as also that of the germinal vesicle, he gives the name of germinal vesi- 

 cles ; thus he says, " the germinal vesicles of the abortive ova (i. e. the 

 vitelligenous cells) become filled vrith a colourless, more or less finely 

 granular fat, and sooner or later lose their nuclei " (I. c. p. 192). 



§ Lubbock (On the Ova and Pseudova of Insects) is of opinion that 

 the vitelligenous cells and the germinal vesicles are only altered epithe- 

 lial cells. His "vitelligenous cells"' become converted into the ova in the 

 following way : — The nucleus of a cell of the kind becomes converted 

 into the germinal vesicle by the later development of the germinal spot 

 (nucleolar corpuscle) ; the membrane of this cell disappears, and the 

 vitellus collects upon it, having been secreted by other but similar vitel- 

 ligenous cells ; and finally the vitelline membrane is developed. He has 

 found this to be the case also with the pseudova ; but here he could not 

 attain certainty as to the genesis of the germinal vesicle (Report by Dr. 



