NARCOMEDUSAE 91 



proboscis, and the largest of them is a well-developed small medusa, not far from liberation. A fifth 

 cluster has accidentally been detached and was found loose inside the bell cavity of the host. Besides 

 the primary individual the cluster consists of two young buds without an umbrella, but each with a 

 long proboscis, and one medusa in an advanced stage of development (PI. VII, fig. 4). It is 07 mm. 

 in diameter ; the jelly is fairly thick in the marginal lappets as well as in the central part of the umbrella. 

 The eight marginal lappets are somewhat longer than broad, ovate in outline and somewhat pointed 

 at the end, the peronia are deep in their proximal part, considerably broadening outwards. A peri- 

 pheral canal is present. The 8 tentacles are directed downwards, tapering in thickness and reaching a 

 little beyond the bell margin. Each lappet carries three otoporpae, the two lateral ones are about as 

 long as the lappet, the median one reaches almost to the summit of the exumbrella and runs along 

 an elevated and fairly sharp keel. Only the median sensory club is developed; it is comparatively 

 large. The velum is broad. The proboscis is very long, conical in its basal part. 



I am inclined to think that these larvae belong to Pegantha triloba ; the ovate, pointed outline of the 

 marginal lappets, the very long otoporpae, and the keels on the exumbrella point in this direction, 

 and apart from the proboscis (which is retained as long as the young medusa is attached to the cluster) 

 they are very like the young medusa, 2-5 mm. wide, of this species, figured by Bigelow (1909, PI. 16, 



fig- 3)- 



Attached to Rhopalonema velatum 



(PI. VII, figs. 5-7) 



St. 250. 17. vi. 27. 36° 09' S, 05° 33' W. Net: TYF 300(-o) m. 



St. 254. 2i.vi. 27. 35° 04' S, 02° 59' 30" E. Net:TYF200(^)m. 



St. 679. 29. iv. 31. 26° 06° 30" S, 30° 06' 15" W. Net: TYFB 300-0 m. 



These localities are between South Africa and the southern part of Brazil. 



In each of these localities one specimen of Rhopalonema was found infected with clusters of narco- 

 medusa larvae, attached to the subumbrella near the base of the manubrium by means of the capitate 

 tentacles of the primary individual of each cluster. The hosts are much degenerated, having lost almost 

 all their organs; in the specimens from Stns 250 and 254 the manubrium is retained; gonads and 

 radial canals have entirely disappeared in all the specimens, but in the specimen from St. 254 the 

 canals are regenerated in a very irregular way. Traces of the marginal tentacles may be discerned. 



Each specimen carries one cluster of larvae attached near the base of the manubrium, and one of 

 the medusa buds is always much further developed than the others in the same cluster. 



The cluster of larvae from St. 250 (PI. VII, fig. 5) consists of one well-developed medusa with a 

 long proboscis and with elongated, pointed tentacles; two small buds, each with a long proboscis but 

 with only a slight indication of the future umbrella; and in addition an undetermined number of very 

 small knob-like buds. The primary individual (the stolo-prolifer) has four tentacles. 



In the cluster from St. 254 (PL VII, fig. 6), one medusa is in an advanced stage of development, 

 the proboscis is fairly short, the tentacles have not yet attained their pointed shape but are knob-hke. 

 On the top of the medusa three very small buds are seen without any indication of umbrella, two of 

 them with a short proboscis. The stolo-prolifer has six tentacles of somewhat different size. 



The cluster from St. 679 (PL VII, fig. 7) is in a very early stage of development. There are only 

 two buds, one much larger than the other, both with a proboscis but no umbrella; the stolo-prolifer 

 has three tentacles, and in this cluster it is clearly seen that the buds, which are destined to become 

 medusae, are derived directly from the stolo-proUfer. 



Before the liberation, the medusa has 11 short, pointed tentacles, all of equal size, directed down- 

 wards. The eleven marginal lappets are square, separated by fairly deep and narrow peronia; each of 



