THE CALCIFEROUS GLANDS OF EARTHWORMS. 
473 
in section ; the junctions of the sinuses in the lamellae with the outer, or general gut 
sinus, are triangular (per. sin., fig. 13). 
Nuclei are occasionally seen in the sinuses of the lamellae — flattened against the 
basement membrane of the epithelial layers, and almost unaccompanied by proto- 
plasm (n.,. fig. 13) ; or, it may be, more ovoid in shape and accompanied by a certain 
amount of protoplasm. Much flattened nuclei may be seen, without any protoplasm, 
between the two layers of basement membrane in the axis of a lamella, where the 
sinus is only potential. Nuclei, flattened or rounded, and without or with accompany- 
ing protoplasm, are to be seen in numerous places on the wall of the general gut 
sinus between the layer of tunnels and the muscular coat of the oesophagus ; but 
these are very far from forming a continuous investment. 
The Posterior Portion of the Gland. — The tunnels become lower in the next 
segments (xii and xiii), and lower still in xiv ; they disappear altogether in front of 
septum 14/15. In the hinder part of the gland the epithelial lining of the oesophagus 
becomes regularly ridged longitudinally once again. 
The lumina of the tunnels are small, and their roofs (toward the oesophageal 
cavity) are more often definitely closed by the opposition of the cells constituting 
their sides. The nuclei between the two layers of a lamella are few. 
There is no evident communication between the cavities of the tunnels and that 
of the oesophagus in the posterior part of the gland ; we cannot definitely state 
that there is no possible passage from the one to the other, as a few sections are 
damaged. The point is again referred to further on. 
The Adult Helodrilus caliginosus. 
A series of transverse sections of a specimen fixed in sublimate and acetic acid, 
and stained in Delafield’s hsematoxylin and eosin, was compared with the above. 
The structure is identical with what has been described already, except in a 
few details. 
The epithelium in the anterior half of the oesophageal pouches is more ridged 
than in the young example ; and the cells here are more markedly columnar — more 
like those of the oesophagus proper, the nuclei being oval to rod-like. The nuclei of 
the cells, however, stain less deeply, and so are not so sharply differentiated from 
the cell-body, compared with those of the proper oesophagus. 
The roofs of the tunnels are closed by a cell ; or by extensions of the cells at the 
sides of the tunnels which fuse together over the roof ; or by an indefinite fibrous 
or granular extension of the sponge-work of the deeper layers of the oesophageal 
lining ; or, finally, the roof may not be completely closed, and the cavity of the. 
tunnel may apparently communicate with the spaces of the loose sponge-work 
just mentioned. 
The central ends of the sinuses in the lamellae are dilated, as in the young 
example ; but here the dilatation is triangular in shape, not oval ; the base of 
