36 Verm. 
VERMES. 
tudinal ridges, which project from the margin of the germinal band on 
each side. The lateral body-cavities persist, and the funnels of the 
nephridia eventually open iuto them. They are, therefore, primary 
coelom ic cavities, and not secondary, as Bourne thought. At a later 
period, after the cells of the nephridial loops have become perforated, 
the two lateral contractile blood-vossels arise, perfectly distinct from the 
coelom. They appear first in the region of the oesophagus, either through 
a splitting of the mesoblast in the above-mentioned lateral ridges, or 
from the remains of the segmentation cavity which are to be found in 
this region. The lateral coelomic cavities meanwhile divide themselves 
each into two : the anterior portion remains empty and the posterior 
contains the nephridial funnel. The two portions remain connected by 
a small canal. They also remain connected with the median ventral 
cavity, which becomes almost filled up by the nerve-cord. 
After the larva has hatched from the cocoon, the lateral cavities com- 
mence to enlarge. At an early period the epithelium of the lateral 
cavities and of the canals connecting them with the ventral cavity give off 
large round cells into the cavities themselves, which are indistinguishable 
from the cells of the gelatinous tissue above mentioned. They are most 
largely developed in an early period of the post-embryonic development, 
and eventually become reduced to a thin cell-layer, which takes the place 
of the original somatopleura and splanchnopleura. This is how Bourne 
came to think that the lateral cavities arose from the botryoidal tissue. 
The canal system of the botryoidal tissue arises from the large round 
cells, which become perforated in an analogous way to the cells of the 
nephridia. The latter arise in a similar way to that described by Bergh 
for Oriodrilus and Lumbricus. They appear at first in the form of large 
round cells (Trichterzellen) at the hinder ends of the somites. These bud 
off cells posteriorly, which arrange themselves in series. The nephridial 
loops are thus formed by continued division from the “ Trichtorzollen. ,, 
The funnel cell (Trichterzelle) itself next gives off cells which surround 
it in a circle. This is the first beginning of the funnel proper. A.s these 
latter cells increase in number, the original large “ Trichterzelle ” be- 
comes no longer distinguishable. As previously described by Bergh, the 
contractile end-vesicle of the nephridium arises by invagination of the 
epidermis, and has no homology in the Lumbncidce. The ovary arises on 
each side from the splanchnopleur of the canal which connects the lateral 
somite with the ventral coelom. It lies between the sixth and seventh 
ganglion. The cavity, in which the ovary lies on each side, widens out 
and bdcomes separated from the ventral coelom, and is now a complete 
cavity by itself, viz., the ovarial cavity. Each ovarial cavity next grows 
ventrally towards the middle line, under the nerve-cord. They meet an 
invagination of the epidermis, which forms the oviduct and genital pore. 
The testes develop later than the ovaries, and arise on each side as a 
longitudinal cellular band, which has formed itself by the fusion of seg- 
mental proliferations of the peritoneum of the lateral coelom. The 
genital band then constricts itself off from the coelom and comes to lie 
