DEGENERATION OF THE EGG-CELLS OF THE GASTROPODS. 
285 
egg-cell of Helix arbustorum. The • cavity between the. wall of the geni¬ 
tal gland and the ^gg represents a part of the blood lacunes in which 
amoebocytes are to be seen. The wall of the lacune turned toward the 
egg-cell is broken through, therefore the amoebocytes are not closed 
from the egg-cell, in consequence of which the amoebocytes can advance 
till the cytoplasm of the egg-cell. When tracing further the fate of 
the egg-cells and that of the amoebocytes associated with the former 
it appears that the number of the amoebocytes, migrated into the 
interior of the egg-cells, constantly increase, and in proportion to their 
number, the mass of the egg-cells decreases, and signs of its dege¬ 
neration begin to manifest themselves, i. e. the amoebocytes become 
transformed into phagocytes, and the process is a typical phago¬ 
cytosis. 
The phagocytic process is more sharply to be seen on fig. 2, 
PI. VII, which exhibits a group of egg-cells of Neritina danubialis 
affected by phagocytes. The phagocytes penetrate into the cytoplasm of 
the egg-cell from the cavities remaining between the ova (PL VII, fig. 2, 
left), and some of them — as is to be seen on fig. 2 — penetrate 
deeply into the interior of the cell-body. From the cytoplasms of the 
affected egg-cells there remains only a granular-fibrous netlike structure 
which is always a typical result of their phagocytosis. As is to be seen 
on the figure, the formation of the fibrous structure coincides with the 
limit of the advance of the phagocytes. But the egg-cells demonstrate 
also other signs of degeneration : the cell membranes are dissolved at 
the place of infection, which results in the flowing together of the cyto¬ 
plasm ; the nucleus of one of them (upper side, in the middle) becomes 
decomposed, but also the symptoms of the degeneration of the cells 
lying on the right side can be established from the fact of separation 
of the chromatic and achromatic substance of the nucleolus. 
Not only the amoebocyte-phagocytes but also the germ cells, i. e. 
spermatocytes and spermatides (PI. VII, figs. 4—5), as well as the nearly 
definitely developed spermatozoa (fig. 3) destroy the egg-cells. During 
the growth period, as is well known, the spermatocytes and spermatids 
need very much material for which purpose the substance of the egg- 
cells furnishes very much, and easily utilisable matter. To nourish the 
developing spermatozoa other cells are originally destined, i. e. the 
basis cells which are equivalent to the SERTOLi-cells of the testes of 
Mammals, but the degenerating egg-cells are in some respects more 
important nourishers of the spermatozoa, partly since in some cases 
(Succinea) the basis cells are not sufficient to nourish the great num¬ 
bers of spermatozoa, and partly since the egg-cells have much more, 
