970 NOTES ON A BEROID OF PORT JACKSON, 



the top they diminish very rapidly in width whilst the edges 

 are straight and but slightly converging towards the mouth- 

 pole, so that the whole resembles a gothic arch. The surface 

 of the broadsides is slightly retracted between every pair of paddle 

 ribs, so that the six broad stripes thereof appear concave. The 

 surface of the narrow side is convex. 



raddle- Ribs. 



The eight paddle-ribs aie not of equal length as the four 

 which lie nearest to the stomach-plane, circumscribe the flaps 

 whilst the four others diverge but slightly from the shortest 

 meridian. They are convex in their distal part. Towards the 

 mouth the eight paddle-ribs run almost parallel. Also herein Neis 

 resembles the Lobatee more than Beroe. The difference in length 

 of the aboral parts of the paddle-ribs observed in the Lobatas 

 is even greater in Neis, so that it might, as far as the paddle-ribs 

 are concerned, be considered as a transition form between Neis 

 and Beroe. 



Nerve Centre. 



The organ of sense at the aboral pole does not show any particular 

 peculiarity, it lies of course in the saddle between the flaps. The 

 Pole fields with their fringes lean on the slopes of the flaps 

 and turn their faces towards each other. They are 2 mm. long, 

 1-| mm. broad and differ only in so far from the corresponding 

 organ of Beroe as the fringes are ramified only in the proximal part 

 and even there only slightly. The fringe on the distal part consist 

 of simple finger-shaped excrescences. I have studied the minute 

 structure of this organ by means of sections. 



The results I have arrived at corroberate the statements of former 

 investigators in particular those of Richard Hertwig (6, p. 339, ff) 

 and Chun (3, p. 165-167). I find that the fringes in especial are 

 clothed with a high Epithelium which consists of broader ciliated 

 cells and slender nervous, sensitive elements. This Epithelium 

 resembles that of the extreme zone in the mouth margin and we 

 shall speak of it again below. 



