49 
and delicately rose-coloured after the pierocarmine reaction. The 
cells composing the walls have a decided resemblance to vegetable 
parenchyma, the protoplasm has retired to a small area, whereas 
the nucleus is applied to the wall of the cell (fig. 53). It is not 
a simple tube but visibly a glandular arrangement around a series 
of central — generally slitlike — cavities, communicating with 
each other and leading outwards. Fig. 52 shows the way in which 
these slits are distributed and intercommunicate. It shows at the 
same time that the simple cellular character only persists in the 
layer immediately coating the internal cavities, whereas connective 
tissue appears to play a more prominent part in the deeper layers. 
In addition to the nuclei of the cells which are faintly stained, 
more strongly coloured nuclei of such tissue, which seems also 
to form the supporting stroma, are found distributed amongst the 
cells. The epithelium clothing the internal cavity is ciliated too 
and the fine granular secretion evidently finds its way towards 
the central cavity along very minute interstices between the ciliated 
epithelial cells. Exteriorly there is a muscular coat in which cir- 
cular fibres play the primary (fig. 52, mt), longitudinal ones the 
secondary part. Numerous radial muscles suspend the apparatus 
to the body-wall.e On the whole the sections through this organ 
have a strong resemblance to those through the albumen-gland of 
other Gasteropods which I have been able to compare. 
The walls of this tube retain the character just described down 
to the spot where a strong muscular constriction mc divides the 
bodiess AR A’R/ into an anterior and a posterior portion. In 
the posterior half that now follows the parenchymatous aspect of 
the walls ceases. The folds are very deep still (fig. 32) but all 
of them more strietly longitudinal. The ciliated epithelium persists 
but the contents of the cells constituting it are more regularly distribu- 
ted throughont the cells and at the same time more granular. The 
 nucleus is rarely visible. Under these ciliated cells a high multi- 
cellular epithelium is situated with elongated cells and very distinet 
nuclei, upon which the layer of ciliated cells just mentioned is 
closely applied (fig. 54). This multicellular layer rests on the mus- 
HUBRECHT, Proneomenia sluiteri. d 
