224 ANGELO ANDRES. 



ridse.^ (e) Some show an irregular outline, occasionally a 

 nucleus, and always intercommunicating prolongations 

 (fig. 15). Thus we have a system of canals ffig. 16) exca- 

 vated through the whole internal moiety of the mesoderm, 

 the mesentery, as well as the body wall, and which are con- 

 tinuous from the parent to the buds ; in the spongy region 

 the canals become larger and larger, and get a mucous layer ; 

 the whole system communicates through very small openings 

 with the gastro-mesenteric cavity.^ 



Here I again call attention to the close relation of this 

 polyp with Antipatharia and Alcyonaria. Though this 

 touches very near the two important questions of phleben- 

 terism and of the origin of the coelome, their discussion is 

 not my present task. 



The fibres are of three kinds — (a) thick, highly refracting 

 fibres, which are sometimes single (fig. 17), sometimes in 

 bundles (fig. 17), and in this case they have a transverse, 

 circular arrangement ; (b) thin, almost invisible fibres, which, 

 like the former, may be single or form bundles ; in one case 

 they are straight or wavy, simple or bifid (fig. 18), in the 

 other always simple (fig. 18) ; (c) the third kind is of pseudo- 

 fibres, viz. of weak, refracting, convoluted forms, which 

 occur in the median portion of the mesoderm (fig. 19). 



The muscular layer (fig. 9, e) is well developed and pre- 

 sents spindle-shaped mono- or binucleated elements (fig. 20); 

 it is more or less conspicuous, everywhere interposed between 

 connective tissue and endoderm. 



The mucous layer (fig. 9,/"), or endoderm, consists of cells 

 very irregularly heaped together. These cells are loosely 

 connected, and therefore preserve their round shape ; their 

 nuclei, and often their nucleoli too, are strongly refract- 

 ing; nematocysts occur only on the mesenteric filaments; 

 ciliated cells I did not see. 



In the lower portion of the body fundamental gelatinous 

 substance and calcareous deposits predominate. Above, on 

 the contrary, the sclerites almost disappear, and the gelati- 

 nous substance becomes thickly crossed by muscular and con- 

 nective fibres of every kind. In the tentacles the ectoderm 

 cells are no longer sunk in groups into the mesoderm, but 

 form a uniform external layer, preserving, however, the three 

 forms already described ; the mesoderm is reduced, but the 

 relative quantity of muscular fibres is increased. In the 

 stomach the wall protrudes towards the cavity with appen- 



1 Lacaze-Duthiers, loc. cit. 



2 Cunt'. KoUiker, 'Actes soc. Ilelv. sc. nat.,' Gcueve, 1865. 



