SYSTEMATIC AND BIOLOGICAL ACCOUNT 91 



In R. plicata the right-hand longitudinal hydroecial canal of the bract is relatively much longer than 

 the left. 



The caducous, larval nectophores grow to a diameter of at least 12 mm. Some of the first known 

 larvae of this species, together with at least one eudoxid, were taken by ' Research ' in the Bay of Biscay 

 in 1900; but all were recorded as larvae of Hippopodius hippopus. In the larval nectophores the lateral 

 radial canals are somewhat sigmoid in shape and do not meander as in the definitive nectophores. 

 Also there is no descending branch of the somatocyst, so that the attachment of the muscular lamella 

 lies entirely above the junction with the pedicular canal that leads to the nectosac (see Text-fig. 32 A). 



C pa 



Cpo 



Cpa 



~-Cped 



2 mm 



Text-fig. 43. Rosacea plicata. A, B, two views of a larva from 'Discovery II' St. 1617, 395-155 m., X7; 

 C, a second definitive nectophore 32 mm. in length, from the same station, x 4-2. 



The slit-like orifice of the hydroecium is less deep and narrower than its main cavity. The whole 

 hydroecium is reminiscent of the hydroecium in the neotenous nectophore of Nectopyramis diomedeae. 

 A constant character that distinguishes larval nectophores of this species [Rosacea plicata) from those 

 of Hippopodiids is the kink caused by the ' central organ ' in the dorsal side of the hydroecium. The 

 nature of this central organ, which has very little affinity for haematoxylin, borax carmine or Sudan III, 

 is uncertain, but seems unlikely to be yolky. It is very like the ' central organ ' of the eudoxid, which 

 appears to be a development of the small piece of stem that remains after separation of the individual 



