GLANDS OF AUSTRALIAN EARTHWORMS. 137 
amount of connective-tissue in which they run, to separate 
lobule from lobule, at the same time sending branches into them 
between the cells, to which they supply materials for secretion. 
The result of this investigation into the structure of the spermi- 
ducal glands of an entirely different series of species from those 
studied by Beddard, clearly corroborates the statement that 
the more complicated lobate forms are derived in a compara- 
tively simple way from the tubular. 
Acanthodrilus sydneyensis, however, differing as it does so 
markedly from the Acanthodrilide generally, cannot be referred 
to the consecutive series at all. 
Conclusions. 
The following are the more important conclusions arising out 
of this paper :— 
1. That for the glands in question there is a correspondence 
between internal structure and external form. 
2. That there exists a complete series of conditions connecting 
the simplest tubular form with the most complex lobular. 
3. That a cell-lining is absent from the finest terminations of 
the duct. 
4, That the structure of the accessory glands in Diplotrema 
fragilis is peculiar, and that of the spermiducal gland in 
Acanthodrilus sydneyensis unique. 
EXPLANATION OF THE PLATES. 
Reference Letters. 
a.g., accessory glands. 1.'m.', longitudinal muscle-band. 
a.'g.', Upper accessory glands. 1./., lacuna in centre of lebule. 
b.v., blood-vessel. m.b., muscular bulbus. 
ce. columnar epithelium. 2.€., nerve-cord. 
¢l., cuticular layer. p., peritoneum. 
c.m., circular muscle-layer of body- r., Ciliated rosette. 
wall. s., penial seta. 
¢.'m.', circular musele-layer of gland- s.s., setal sac. 
duct. s7r., sperm-reservoir. 
c.t., connective-tissue. sp.d., spermiducal duct. 
gc., gland-cells. sp.'d.', fine branches of spermiducal 
gc.', special club-shaped gland-cells. duct. 
g."'c."', duct of gland-cell. sp.g., spermiducal gland. 
i.m., longitudinal muscle-layer. v.d., vas deferens. 
The outlines of all the figures have been drawn beneath the camera lucida, 
and on pl. 14 the position of the yas deferens is in all cases indicated by dotted 
lines. 
LINN. JOURN.—ZOOLOGY, VOL. XXVIII. 10 
