THE CALCIFEROUS GLANDS OF EARTHWORMS. 
463 
many earthworms, which are in some cases, at any rate, ciliated.” Beddard here 
adds a note, “ In Acanthodrilus antarcticus and in the young of A. multiporus. I 
do not know how far this ciliation is prevalent among earthworms.” 
Eisen is largely concerned with the vascular supply. The blood-vessel supplying 
the sac is single at its origin, where the sac originates from the oesophagus ; it then 
breaks up into branches, which are grouped in bunches; the vessels unite again at 
the distal end of the sac, and in their course are parallel, and do not anastomose. 
The vessels cause the longitudinal ridges of the inner surface of the sac-wall, which 
are prominent, and sometimes so large as almost to divide the pouch into several 
parallel chambers ; the inner lining of the pouch is ciliated. 
Michaelsen, in the course of systematic studies (16, 17), has examined the glands 
of 0. ( Ilyogenia ) calwoodi and O. (I.) africanus, which he prefers to call “ chylesacs” 
(Chylustaschen). In the former species the broad lumen is partly narrowed by 
septa, and contains considerable calcareous masses ; the blood-vessels of the sac 
unite at the free end to form a vessel which then runs freely. In the latter species 
the lumen is divided by a number of septa, longitudinal in direction, which spring 
from the wall and meet in the axis of the sac so as to give a wheel-like appearance 
to a transverse section ; the number of radiating septa may be as many as seven ; 
the external wall as well as the septa are rather thick, and are provided with a 
system of very narrow canals (Chylusgefasse). 
Beddard gives no figure, and Eisen’s figure of a longitudinal section scarcely 
affords a good conception of the essential structure. We therefore give a reproduc- 
tion of a transverse section through the sac of one side of 0. ( Ocnerodrilus ) occidentalis 
(fig. 3), showing the ridges of the interior, and the relations of the blood sinus — an 
extension over the sac of the general gut sinus. The muscular layer over the sac is 
extremely thin, or in places absent ; the sinus is then bounded on its outer side by 
the peritoneal coat, together with a distinct basement membrane. 
We cannot discover cilia within the sacs ; the„ cells may be covered by a Huffy 
secretion, beneath which the surface of the cells is as a rule, though not always, 
quite sharply defined ; or the cells may show on their surface a fine thready ragged- 
ness ; or the surface of the cells may be quite clear of any appendages or adventitious 
matter. 
The neighbouring portion of the oesophagus shows an interesting condition of the 
epithelium (fig. 4). In segment ix, in the part adjacent to the opening of the sacs 
into the oesophageal lumen, and in segments x and xi, the epithelium bears a layer 
of rodlets, 7 p in height, with the usual palisade-like arrangement, practically non- 
staining ; the free border of the layer appears crenulated in the sections. The 
surface of the cells beneath the rodlets stains more deeply than the rest of the cell ; 
in the deeper half of the epithelial layer is a series of oval vacuole-like spaces ; the 
nuclei are round, at the middle of the height of the cells, just superficial to the layer 
of vacuoles. Cell outlines are not distinguishable ; the protoplasm of the superficial 
TRANS, ROY. SOC. EDIN., VOL. L1I, PART II (NO. 17). 71 
