304 TRANSACTIONS LIVERPOOL BIOLOGICAL SOCIETY. 



in some cases the siphonoglyphs were so indistinct as 

 not to be distinguishable from the ordinary longitudinal 

 grooves of the oesophagus, and in other cases some of 

 the ordinary longitudinal grooves were so enlarged and 

 exaggerated as to lead me to think they were true 

 siphonoglyphs. 



The mesenteries are attached lengthwise to the sides of 

 the column, the " complete " mesenteries stretching 

 across and uniting with the oesophagus, the "incom- 

 plete" mesenteries falling short and hanging freely in 

 the cavity. Most of my specimens exhibited twelve 

 pairs of complete mesenteries representing the first and 

 second cycles. There were usually three other cycles of 

 ''incomplete" mesenteries present. This arrangement 

 is represented by the diagrammatic fig. 1, PI. XX. Of 

 the complete mesenteries, two kinds are distinguished by 

 the arrangement of the mesenterial muscles. Each 

 mesentery has longitudinal muscle fibres on the one face, 

 and transverse muscle fibres on the other, forming in each 

 case a slightly raised layer. Each pair of mesenteries 

 has similar muscles on the sides facing each other, that 

 is, projecting into the endocoele or space enclosed between 

 each pair of mesenteries. In all cases except two, it is 

 the longitudinal muscle series which are so arranged, 

 and these two exceptions, which are known as the 

 "directive" mesenteries (PI. XX., fig. 1, d.), have the 

 transverse muscles facing the endocoele or intra-mesen- 

 teric space, and the longitudinal muscles facing the 

 exocoele or inter-mesenteric space. The remaining com- 

 plete mesenteries are known as the " non-directives " 

 (PI. XX., fig. 1, n. cl). 



I have examined 165 specimens of Actinia equina, and 

 out of these, 158 had the arrangement of mesenteries, the 

 number of oesophageal grooves and directive mesenteries 



