LIMNOCNIDA TANGANICiE. 
91 
canal in the higher animals. Every condition of secretory 
activity can be distinguished in these goblet-cells, and they 
have, moreover, a very definite arrangement. The goblet- 
cells furthest from the mouth (fig. 4) stain very deeply with 
haematoxylin and have clear protoplasmic contents. Slightly 
distal to these (fig. 5) we find that these cells have elaborated 
large quantities of mucin, and contain large colourless and 
highly refringent granules of this substance. Finally, at the 
oral extremity of this region the goblet-cells have discharged 
the mucin, and have the characteristic cup-form typical of 
this kind of cell ; except for the basal nucleus and a 
net-work of fine granules they do not stain at all, and thus 
become very conspicuous. 
The ectoderm of the oral region consists of large, low 
musculo-epithelial cells with much vacuolated protoplasmic 
contents ; interstitial cells, with occasional nematocyst-cap- 
sules, occur sparingly. I could trace no stinging-cell battery 
along the edge of the mouth. 
(ii) The Middle Region. 
The middle or gemmiferous region of my specimen agrees 
in structure with that described by Gunther. The structure- 
less lamella is very thin, and both ectodermal and endodermal 
linings high. The latter consists of more than one layer. 
The cells bordering on the cavity of the manubrium are 
elongated with fine granular contents, and obviously corre- 
spond to the similar cells in the oral region; I agree with 
Gunther in thinking that these cells may be provided with 
flagella during life, although I could detect none in my 
sections. 
One or two layers of smaller cells occur at the bases of the 
elongated endoderm cells; they are also finely granular, but 
roughly polygonal in shape, and provided with slightly 
smaller nuclei. 
The ectoderm of this middle region consists of largo 
vacuolated cells without definite cell outlines, between which 
