THE CALCIFEROUS GLANDS OF EARTHWORMS. 
479 
can properly be applied is evident from the fact that it is absolutely continuous 
with the epithelium of the oesophageal pouches, and so with the oesophageal 
epithelium itself. If it were necessary to go further, the constitution of the glands 
in other families would be sufficient as proof of the identity of the epithelium of 
the follicles and of the oesophageal lining. 
We entirely disagree, therefore, with Harrington when he says : “ It must be 
repeated that the first pair of glands are entirely different morphologically from 
the two posterior pairs, and are the only portions of the glandular oesophagus 
which are true epithelial diverticula.” The difference is one of detail only ; the 
ridges of the oesophageal pouches are, in the anterior part of their extent at least, 
parallel to and independent of each other ; further back they fuse at their free 
edges and so form a series of tunnels, 'the so-called follicles of the oesophageal glands 
of segments xi-xiv ; — that is all. 
The same idea runs through the work of Combatjlt : “ L’histologie de l’adulte 
et de l’embryon me semble montrer que le tissu des glandes de Morren est d’origine 
nffisodermique vasculaire.” The difference between the glandular cells and avascular 
endothelium is due “ avant tout” to a difference of technique ; if one fixes by acid 
reagents (Bouin’s solution) the cells, where not destroyed, “ presentent assez bien 
l’aspect de 1 ’ endothelium vasculaire avec lequel elles semblent se continuer ” ; and 
in Phcenicodrilus taste , as described by Eisen, we actually do find the glandular cells 
represented by “ un endothelium aplati tres mince rapellant bien l’endotheiium vascu- 
laire.” There is nothing here that requires further comment however. 
Combault’s views appear to have undergone some change during the progress 
of his series of papers ; thus in a later paper he says that “ chaque feuillet est lui- 
meme constitue de deux assises — l’endothelium vasculaire et l’epithelium branchial.” 
He is speaking of the lamellae of the gland, which he looks on as a respiratory 
organ, and here states that in addition to the respiratory ( i.e . glandular) epithelium 
there is beneath it a vascular endothelium ; the glandular epithelium is not there- 
fore a vascular endothelium. This view is, however, no more admissible than the 
first ; it predicates two cellular layers on each side of the blood film in the 
lamellae, whereas, as we have seen, there is universally only a single layer bounding 
the gut sinus on its inner side — the layer of the alimentary epithelium. That there 
are nuclei on the basement membrane, bathed by the blood stream, is undeniable, 
but they do not form an endothelial layer, and are in no sense a vascular endo- 
thelium. Combatjlt also begins to have doubts as to the mesodermic origin of the 
glandular epithelium : “ II est d’ailleurs tres difficile d’affirmer d’une fa90n precise 
de quel feuillet embryonnaire derive l’organe de Morren.” It is, however, his first 
view — that the glands are mesodermic — that has been laid hold of by the author of 
the elementary textbook quoted in the Introduction, and that, more than anything 
else, we wish to oppose. 
One of Combault’s statements deserves a word of notice ; he says : “ Ddja 
TRANS. ROY. SOC. EDIN., VOL. LII, PART II (NO. 17). 73 
