REPORT ON ACTIXIARIA. 



239 



The absence of ectoderm, however, probably accounts for my 

 failure to find these structures. 



The tentacles are marginal in position and are rather short, 

 tapering gradually to a rather blunt extremity. The)' are 

 arranged apparently in about three cycles and seem to be 

 somewhat irregular in number, the two specimens in which I 

 counted them possessing respectively 51 and 49; this irregu- 

 larity is probably related to the peculiar arrangement of the 

 mesenteries described below. The longitudinal musculature 

 of the tentacles, which is ectodermal, was moderately devel- 

 oped, the mesoglceal processes being higher towards the base, 

 and the radial musculature of the disk was considerably higher 

 at the bases of the tentacles than elsewhere. The disk was 

 smooth and the peristome somewhat elevated in those speci- 

 mens in which it was visible. 



The mouth was more or less circular in shape, the lips 

 being crenated and the gonidial grooves not very well marked. 

 Sections showed that the stomatodaeum possessed several 

 longitudinal ridges, due to thickening of the mesoglcea and 

 producing the crenations of the lips. Two siphonoglyphs 

 were present in all the specimens examined, and others, one 

 or even two. were found in several cases; they were always, 

 however, rather feeblv developed and sometimes hardly dis- 

 tinguishable from the grooves of the general surface of the 

 stomatodaeum. 



The arrangement of the mesenteries was very interesting, 

 so much so as to induce me to give a special description of it 

 elsewhere ('97); I may therefore, confine my remarks here 

 to a general statement of the peculiarities which were found. 

 The mesenteries were arranged in three cycles, only those of 

 the first cycle being perfect. In different specimens, however, 

 the first cycle consisted of either six, seven, or eight pairs, a 

 hexamerous, heptamerous, or octamerous symmetry being 

 thus produced, since the mesenteries of the second and third 

 cycles were arranged in the intervals between those of the 

 first cycle. Furthermore the directives were liable to consid- 

 erable variety both in number and position, specimens having 



