56 THE VOYAGE OF II. M.S. CHALLENGER. 



oesophageal lappets extend downwards, far into the stomach. The upper half of the 

 oesophagus shows about twenty longitudinal ridges which are prolonged lower down into 

 a larger number of smaller ridges. The boundary between the oral disk and the 

 oesophagus is defined by a sharp line. 



The septa (PI. XIII. fig. 9) are very simple in construction, as specially differentiated 

 muscles (retractor and parietobasilar muscle) are wanting, and the two primitive layers of 

 muscles only are present. Transverse muscles, which run oblkmely between the wall on 

 the one hand and the oral disk, oesophagus, and free margin of the septa on the other, 

 extend on one side, and are strongest in the upper and lower third, where their lamellae 

 are repeatedly folded ; on the other side run parallel longitudinal muscles also in a 

 repeatedly folded layer from the pedal disk to the oral disk and the oesophagus. In the 

 perfect septa a small peristomial opening lies hidden in the angle formed by the junction of 

 the proboscis-like part of the oral disk with the oesophagus. 



As may be concluded from the large number of the tentacles, the number of the septa 

 is something quite unusual, even though many of them have stopped growing at a very 

 early stage. The septa of the second and third cycles are perfect as well as the principal 

 septa, and are easily distinguished from one another by the difference in size and by 

 the extent to which they descend on the oesophagus. Of the imperfect septa, those belong- 

 ing to the fourth and fifth orders are still well developed ; after that they decrease rapidly in 

 size, so that the other septa almost come to be mere folds projecting more or less in the 

 angles on the upper and lower end of the wall. This recalls the comportment of the 

 tentacles in which the first four to five cycles are the most easily distinguished. 



In order to obtain a general idea of the aggregate number of the septa, I prepared an 

 intraseptal space of the third order as completely as possible, and made a transverse section 

 through it, which passed through the upper part of the wall and the peripheral part of the 

 oral disk. In this section I found more than sixty separate septa. This would give over 

 1500 septa, or over 700 pairs of septa for the entire animal. There appear, therefore, on 

 the whole, to be eight cycles or 768 pairs of septa. There may perhaps be traces of a ninth 

 cycle, as each interseptal space of the eighth order is furnished with at least three tentacles. 



I can say nothing as to the distribution of the reproductive elements on the septa, as 

 their thin-membraned parts had stuck together and were badly preserved. Some figures 

 which I got in the sections lead me to believe that Antholoba may possibly be herma- 

 phrodite. This would be very unusal, as I have as yet only observed herm aphroditism in 

 Gerianthus and Scytoijhorus. 



Ophiodiscus, n. gen. 



Paractidae with a single corona of long tentacles, which project at the margin of the 

 wall and oral disk, and are only furnished with muscles on the upper side ; wall smooth, 

 with longitudinal furrows, indicating the insertions of the septa ; septa differentiated 



