REPORT ON THE ACTINIARIA. /» 



inasmuch as they are broadest towards the periphery, where they are each divided by two 

 long radial furrows into three ridges, a middle ridge belonging to one of the twenty-four 

 tentacles of the second cycle, and two lateral ridges which pass on to two of the 

 forty-eight tentacles of the third cycle. This division corresponds at the same time to 

 the arrangement of the septa, the twenty-four interseptal spaces are divided in the 

 periphery by the twenty-four pairs of septa of the fourth order into three compartments, 

 an intraspace and two interspaces. 



The number and mode of arrangement of the tentacles may be deduced from what 

 has been said. We find altogether ninety-six tentacles distributed in three rows, twenty- 

 four in the first or innermost row, twenty-four alternating with them in the second row, 

 and forty-eight in the third row. This is best seen if we cut away the tentacles, leav- 

 ing only the short basal stumps (PI. I. fig. 4). The tentacles have a slender shape, 

 diminishing uniformly from the base towards the point ; they are distinctly striated longi- 

 tudinally and perforated at the end by a fine opening ; they are largest in the innermost 

 row, where they attain a length of 2 cm. The longitudinal striation is caused by elevations 

 of the supporting lamella, which are covered moreover with small folds bearing the muscles. 

 The boundary between the oral disk and the oesophagus is only indicated by a slightly 

 swollen Up. The oesophagus has tolerably broad oesophageal grooves and short oesophageal 

 lappets ; it also shows eleven powerful longitudinal swellings on either side (fig. 5). 



The arrangement of the septa is governed by the same principle, which has been 

 akeady laid down as applicable to most Sagartice. Its characteristic is, that only the 

 six pairs of principal septa, of which again two pairs are directive septa, reach the 

 oesophagus. The principal septa are, at the same time, exclusively muscular septa, i.e., 

 they do not develop reproductive organs. Their muscular systems are not very strong ; 

 for example, the parietobasilar muscle is merely a slight fold ; the most distinct among 

 them are the longitudinal fibres, which rise obliquely from the wall and the base to the 

 oral disk. An internal septal stoma is certainly present, but so small as to be easily 

 overlooked ; an external septal stoma is wanting. 



The principal septa are followed by three cycles of imperfect septa ; the development of 

 their muscular system is far behind that of the principal septa, but, on the other hand, 

 they are furnished with reproductive organs (in the present case with ovaries). In each 

 cycle they become smaller, and project less into the gastric space and towards the pedal 

 disk and oral disk. The last forty-eight pairs are hardly recognisable as longitudinal lines 

 on the wall, and merely project as folds in the angles formed by the wall on one side and 

 the oral disk or pedal disk on the other (figs. 4 and 5, h*). The reproductive organs lie 

 highest up, and quite hidden by the oesophagus on the septa of the second order (figs. 

 4 and 5, h 2 ) ; in the septa of the third order they are visible under the lower margin of 

 the oesophagus (figs. 4 and 5, h 8 ), while in the septa of the fourth order they are insignifi- 

 cant bodies, confined to the lowest section. 



