NARCOMEDUSAE 89 



very tiny tentacle is situated; as yet there is no indication of a gastric pouch corresponding to this 

 young tentacle. Between the next two fully developed tentacles, the development has proceeded 

 somewhat further ; a small gastric pouch has been formed, the sling of the canal has come into com- 

 munication with it, the peronium has increased considerably in length, but there is still some distance 

 between the tentacle and the gastric pouch. Presumably each of the two original lappets has had three 

 otoporpae, but the median one has disappeared at the beginning of the formation of the canal sling; 

 when the division is finished and the two new lappets have attained their final width, new sensory 

 clubs and otoporpae will arise, so that there will be two or three of them in each of the fully developed 

 lappets. In this specimen the gonads are in the act of developing, but the folding as seen in larger 

 specimens has not yet appeared; the walls of the gastric pouches are smooth. 

 The total number of tentacles in specimens of different size are as follows : 



Diam. (mm.) 4 5 6 6 7 8 8 8 9 10 17 18 19 22 23 23 29 29 31 33 46 48 50 58 



No. of tentacles 9 11 10 14 10 10 13 17 12 20 13 18 20 20 18 19 23 29 20 26 20 19 27 24 



In some of the specimens the tentacles are greatly extended, being about as long as the diameter of 

 the umbrella. When sensory clubs are retained (PI. VII, fig. 2) they are seen to be about 56 /x in length 

 and 26 fi in width ; the statolith, which has been dissolved by the formalin, has been deposited in 

 one fairly large space in the terminal end of the club. The sensory club is situated on a small epithelial 

 cushion. The otoporpa is hardly broader than the club and about three times as long. 



In all the present specimens the two canals flanking each of the tentacles are at least as wide as the 

 corresponding gastric pouch. May it not be something like this that Haeckel has seen in his genus 

 Cunissa, in which 'jede radiale Magentasche an ihrem Distal-Rande in 2 Lappentaschen sich spaltet'? 

 C. duplicata, however, cannot belong to either of the two species of ' Cunissa ', none of which have 

 been found since they were described by Haeckel. 



Distribution. Cunina duplicata, previously known from only one locality south of the Cape Verde 

 Islands, occurs in the central and southern parts of the Atlantic between the Cape Verde Islands and 

 South Georgia, and off the southern part of the east coast of Africa. It apparently belongs to the 

 upper layers, though in the southernmost locality it was taken in a haul between 1600 and 1000 m. 



COMMENSAL LARVAE OF NARCOMEDUSAE 

 Larvae of Narcomedusae were found attached to the subumbrella of the following species of medusae : 

 Bougainvillia platygaster, Rhopalonema velatmn, Rhopalonema funerarium and Pantachogon haeckeU. 

 The larvae evidently belong to four diflFerent species. In all, the development proceeds in a very 

 similar way which, however, diff^ers fundamentally from the development of the other narcomedusa- 

 larvae previously described. Larvae attached to the subumbrella of other medusae and feeding by 

 inserting their prolonged manubrium into the stomach cavity of the host were described by McCrady 

 1856 and 1857, Brooks 1886, Wilson 1887, and Bigelow 1909, while a general survey of the develop- 

 ment of narcomedusa-larvae was given by N. J. Berrill in 1950. In all these cases, it is stated by the 

 authors that the larvae propagate by budding, but the primary individual, as well as all the others, 

 develops into a medusa, so that (as emphasized by Brooks) there is no true ahernation of generations. 

 In all the present cases, on the other hand, the development is a true metagenesis, as will be seen from 

 the following description. 



The larvae are collected in clusters attached to the subumbrella of the host by means of a number 

 of threads, which are really the tentacles of the primary individual of the cluster. These tentacles are 

 solid, with an endoderm consisting of one row of disc-like cells and terminating in an adhesive, 

 knob-like expansion studded with nematocysts. The body of the primary individual is merely a 



