FUNICULINA QUADRAXOULAIUS. 18 



tentacles in the livinj^ animal are effected, and alRO, in part, the 

 retraction of the tentacles when disturbed. 



The endoderni does not differ markedly from that of the body- 

 wall : it consists of a single layer of columnar cells, often swollen at 

 their inner ends. In the cavities of the tentacles, the size of which 

 varies much with the extent to which the tentacles are expanded, verj' 

 numerous spherical nucleated cells occur: these are always in close 

 contact with the endoderni cells, but whether they properly belong to 

 the endoderni or not we have been unable to determine. They may 

 perhaps be described as mucus cells. 



The pinnules have the same structure as the tentacles. Each 

 is hollow, its cavity opening into that of the tentacle (Figs. 

 10 and 11), and its wall consisting of ectoderm, mesoderm, and 

 eudoderm, having the same structure and proportions as in the 

 tentacles, differing only in being of less thickness. 



d. The Stomach. — The mouth is not circular, but, as in the majority 

 of Actinozoa* a transverse slit. The section drawn in Fig. 12, though 

 taken a short distance below the mouth, shows this character very well. 

 The direction of the axis of the mouth, which is a constant one, we 

 shall refer to after considering the arrangement of the mesenteries. 



The mouth leads by a short cesophagus into the stomach (Fig. 10 n), 

 the walls of which are thrown into transverse folds, as shown in the 

 figure : these folds become much more marked when the tentacles are 

 retracted, the whole stomach being then shortened by the approxima- 

 tion of the folds, somewhat after the manner of a concertina, and thus 

 providing space within the calyx in which the retracted tentacles are 

 lodged. At its lower end the stomach opens into the b^ dy cavity by a 

 slit-like orifice, the direction of which corresponds to that of the 

 mouth. 



The stomach-wall consists (Fig. 10) of (1) an inner lining membrane 

 which at the margin of the mouth becomes continuous with the 

 external ectoderm, and is therefore described as ectoderm ; (2) of a thiu 

 mesoderm ; and (3) of an outer laj-er or endoderin continuous with that 

 of the tentacles and of the bod\'-wall. 



The ectoderm (Figs. 10 and 13, w) is a thick layer, consistmg' of 

 much elongated columnar ciliated cells, between which are other 

 elongated cells with a very granular appearance, and probably of a 

 glandular nature : at the inner or free surface are seen at intervals 

 what appear at first sight to be clear spaces, but which are almost 

 certainly cells similar to those described in Anemones by the Hertwigs 

 as mucous cells, f The deepest or outermost part of the ectoderm 

 contains fusiform and spherical cells imbedded between the bases of 

 the longer ciliated and glandular cells. 



* Vide Gosse ; Heider, etc., op. cit. 



+ O. imd R. Hertwig: Op. cit., pp. 58-60. and Taf. III., Fig. 6, where the two 

 kinds of gland-cells, viz., granular and raucous, are described and figured. 



