On the other hand, the ejaculatory duct with its verticillate sac in the male of Cypris and other genera is a feature scarcely less remarkable.
In Clausilia, according to the observations of C. Gegenbaur, the primitive shell-sac does not flatten out and disappear, but takes the form of a flattened closed sac. Within this closed sac a plate of calcareous matter is developed, and after a time the upper wall of the sac disappears, and the calcareous plate continues to grow as the nucleus of the permanent shell.
To the left of the vena cava is the Spigelian lobe, which lies in front of the bodies of the tenth and eleventh thoracic vertebrae, the lesser sac of peritoneum, diaphragm and thoracic aorta intervening.
I, Aperture connecting the small sac with the pericardium.
The larger renal sac (remarkably enough, that which is aborted in other FIG.
Outline of part of the renal sac (nephridium) below the surface.
Sperm, spermatheca; sp. o, its external orifice; sp. sac, spermathecal sac; ov, sac containing ovary;.
Pore leading from the pericardium into the glandular sac of the left nephridium.
In this duct and sac the spermatophores received in copulation from another snail are lodged.
The left side so as to open the f, Probe introduced into the left non-glandular sac of the reno-pericardial orifice.