PROSTATE GLANDS OF THE EARTHWORMS OF THE FAMILY MEGASCOLECIDiE. 451 
and of the body-wall. The tubular form, from which the lobate has been derived, 
will hardly own a different origin, though we have not been able to establish this 
by following the development, having had no young specimens of Eutyphoeus at 
our disposal. 
But the adult form of another genus has, it seems to us, provided us with an 
unmistakable indication of the mesodermal origin of the tubular prostate. 
The tubular prostate occurs throughout the Megascolecid sub-family Trigastrinse, 
to which the genus Dichogaster belongs. In two small specimens belonging to this 
genus, sectioned by one of us in the course of systematic work (one belonging to 
D. malayana, from Negyatankaray in Southern India, and one to D. affinis, from 
Ceylon), the prostates appear as small, almost straight, tubular structures, each 
confined to a single segment, and attached to the posterior septum of the segment 
in which they occur (xvii and xix). The condition is illustrated in fig. 9. There 
seems no reason whatever for assuming a secondary attachment of the prostates to 
the septa, and the appearance constrains us to suppose that the gland was derived 
by proliferation from the septum — from the peritoneal covering, that is, or from 
the connective tissue. 
The Prostate in the Young Ocnerodrilus. 
Though not in Eutyphoeus , we have been successful in obtaining an early stage 
in the development of the tubular prostate — from some small non-sexual specimens 
of Ocnerodrilus occidentals. The tubular prostate is found throughout the Ocnero- 
driline sub-family of Megascolecidse, and we sectioned some of the above material 
in the hope that an early stage in the development might possibly be obtained. We 
were successful in one case. The first rudiment of the gland was present, in a very 
early stage ; the whole only takes up three to four sections. 
The gland (fig. 10) consists of deeply staining nuclei in a small amount of proto- 
plasm, which also stains rather deeply. The mass is already hollow, and around 
the small central cavity the nuclei are arranged in two series, one bounding the 
lumen, and the other, less regular, outside these. The layer bounding the lumen 
is continued outwards to the base of the surface epithelium ; the outer cells shade 
off into a looser aggregate, the elements of. which are apparently similar to those 
of the peritoneum and intramuscular connective tissue. On one side of the 
specimen the epidermis is already indistinctly Canalised ; on the other there is 
only a slight dimpling of the surface. 
There is no evidence of proliferation of the surface epithelium. The newly form- 
ing duct joins the surface cells, but the two can be distinguished by their nuclei — 
homogeneous and elliptical in the one case (the embryonic cells of the duct), spherical, 
almost clear, with central chromatic granule in the other. The height of the surface 
epithelium is four times the greatest measurement of the prostatic cells. 
TRANS. ROY. SOC. EDIN., VOL. LII, PART II (NO. 16). 
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