GENERATIVE ORGANS OF NEMATOIDA. 293 



each of them, without the individual formations ever being united 

 in any way by a solid axis. They do not yet possess a vitelline 

 membrane, as this only makes its appearance after fecundation. 

 The above-mentioned authors, therefore, certainly admit the 

 possibility that the first germinal vesicles might perhaps increase 

 in a mother-cell in the interior of the blind extremity of the 

 ovarian tube, but assert that the individual germinal vesicles, 

 whether isolated or grouped several together, do not become 

 enclosed in a vitelline membrane till a very late period, arid that 

 the latter is by no means a residue of the mother-cell, and the 

 cause of the production of the bunches of eggs of which Meissner 

 speaks. 



2. The Vitelliyene (Dotterstock). — It is rather long, and when, 

 as in the Ascarides for example, its walls are tolerably thick, it is 

 smooth externally ; but when, as in Mermis, it has yielding walls, 

 it is alternately pushed out in a racemose form and constricted. 

 In the first kind, which we find in the Ascarides, the groups or 

 racemes of ova which are arranged in the form of flat, circular, 

 stellate discs, furnished with as many rays or sectors as the 

 mother-cell has daughter-cells, are pressed against one another 

 like layers, in such a manner that they exhibit the disposition of 

 a galvanic battery, or of the pieces in a roll of money. In Ascaris 

 lumbricoides, the mother-egg, with the daughter-eggs, has the 

 appearance of a wind-mill, looked at from the front ; regarded 

 separately, each daughter-egg forms an isosceles triangle, like the 

 sail of a wind-mill, and communicates at its apex with the mother- 

 cell or mother-egg. In the so-called vitelligene, or yelk-producing 

 organ, on the inner surface of which, according to Nelson 

 and all subsequent observers, there are ridges of a finely granular 

 appearance, running longitudinally in a slightly spiral direction, 

 the vitelline mass is added to the eggs. According to Nelson, 

 Thompson, and Bischoff, the vitelline mass is deposited from 

 without upon the free germinal vesicle. The small, dark, vitelline 

 granules, which constitute the most striking part of the vitellus, 

 appear first of all as a deposit on the outer surface of the ger- 

 minal vesicle, and even subsequently, the vitellus, wherever it 

 may be produced (whether from the peculiar projections of the 

 vitelligene, or from the fluid surrounding the germinal vesicle), 

 is nothing but an accumulation from without, which is by no 

 means held together by a peculiar membrane, but only by a 

 gelatinous, clear, connecting substance, as is the case also, accord- 



