PROSTATE GLANDS OF THE EARTHWORMS OF THE FAMILY MEGASCOLECIDHS. 437 
inner region ; they stain less deeply than these, and a nucleus is visible. Between 
the two layers a slight development of connective tissue is visible, and a layer of 
blood vessels. Externally the gland is encased by connective tissue, beneath which 
masses of yellow-brown pigment spots are sometimes seen. 
Beddard, in his monograph (l), gives a short description of the tubular prostate 
on the above lines, mentioning a peritoneal membrane on the outside. 
Miss Sweet, in her study of the prostates of Australian earthworms (7), describes 
first the macroscopic characters of the male organs in a considerable number of the 
Megascolecinse. In the account of the histology of the tubular forms she states that 
the central lumen is lined by an epithelium of ordinary columnar cells with a nucleus 
at the inner end of each ; sometimes the lining is of cubical cells ; outside the lining 
epithelium is often a small amount of connective tissue with blood vessels. The 
bulk of the wall is composed of granular gland cells with pear-shaped outer end, and 
long, narrow, duct-like inner end which opens into the lumen between the cells of 
the columnar lining, sometimes singly, sometimes in groups. In some forms there 
are seen a number of cells, staining much more with methylene blue, more granular, 
and forming a more or less distinct layer at about one-half the depth of the wall ; 
these have a more rounded, club-shaped end than the ordinary form of gland-cell. 
Fine capillaries are present among the glandular cells. Acanthodrilus sydneyensis 
departs from the type above described. 
We may so far anticipate our own conclusions as to say that in Eutyphoeus the 
structure of the prostate shows a considerable resemblance to that of Megascolides 
australis as described by Spencer. The inner layer of cells can here, however, 
scarcely be said to form an epithelium — the cells are much too sparse ; nor is there 
a definite connective tissue or peritoneal covering, as claimed both by Spencer and 
Beddard. The very well-marked epithelial lining figured by Miss Sweet for the 
tubular glands of the Megascolecinae is altogether absent in Eutyphceus, certainly 
so when the gland is fully formed and. actively functioning. 
Beddard (l), resuming the histological structure of the lobular prostates, states 
that the ductules are lined by a low columnar epithelium, which does not ever 
appear to be markedly glandular ; attached to these tubes are groups of pear-shaped 
cells massed into bundles, whose fine processes seem to open into the lumen between 
the non-glandular cells which line it. The whole is covered by a fine covering of 
peritoneum. There is no essential difference between this type of gland and the 
tubular, and there seem to be glands with an intermediate character. 
According to Miss Sweet, each lobule has a typically radiate appearance, with 
sometimes a small lacuna in its centre ; this is, however, generally obliterated by 
the approximation of the inner ends of the cells. In very rare cases a communica- 
tion can be traced between the lacuna and the terminal branch of the duct ; in no 
instance was any epithelium to be seen around the central lacuna. 
Here again, in Pheretima, we miss the general peritoneal covering described by 
