SYSTEMATIC AND BIOLOGICAL ACCOUNT 99 



Material. Bermuda, Coll. Wm Beebe; 1645-1828111., two pairs of nectophores (separated), 

 two large nectophores, one eudoxid. 



'Discovery II' Station 695, 370-0 m., one connected pair, 1 cm. in diameter. Station 2636, 950- 

 550 m., one pair of nectophores (separated) with stem groups. Station 2639, 1200-600 m., one pair 

 of nectophores (separated). 



Distribution. Hitherto the species had been found only in the Atlantic Ocean. 'Discovery II' 

 Station 1580 (450-0 m.) in the Indian Ocean. 



Holotype. One larger nectophore — a smaller, now detached, probably belongs — with attached stem 

 groups, 'Discovery II' Station 2636 (Pis. VI, VII; Text-fig. 48 A). Brit. Mus. (Nat. Hist.) Register 

 No. 1952. 11. 19. 6. 



HIPPOPODIIDAE 



Hippopodius hippopus (Forskal), 1776. 



The four peculiar teeth of the nectophore of H. hippopus, and probably the two of Vogtia glabra are 

 homologous with, and vestiges of, more numerous teeth found in other more spiny species of Vogtia. 

 Bigelow ( 1 9 1 1 b, p. 2 1 1 ) states that the nectosome of Hippopodius hippopus is not effective as a swimming 

 organ. Certainly, if retracted preserved nectophores alone are studied, this is an understandable 

 deduction to make. But in life the upper, oral side of the nectosac has a very different appearance, 

 and takes part in a scooping action (as it fills with water) reminiscent of a movement of the appendages 

 of a cirripede. There is a reduplication of the dorsal part of the nectophore (see Chun, 1897a, fig. 11) 

 which gives the thin upper wall of the nectosac freedom of movement. Observation with a lens 

 showed me that it is chiefly the upper, dorsal half of the subumbrellar musculature that contracts. 

 There is a distinct line of demarcation visible between the velum and subumbrella. The whole 

 swimming action of the nectophore is reminiscent of Rosacea cymbiformis. 



The contraction of the nectosac of Hippopodius hippopus appears to be an advance upon that of 

 Rosacea. The extent of the living nectosac of Hippopodius hippopus would surprise an observer who is 

 familiar only with preserved and contracted material. I refer elsewhere (p. 138) to the 'smoky' 

 appearance assumed by nectophores of this species when they are stimulated, a phenomenon mentioned 

 also by Korotneff (1884) and by Chun (1888 a). When undisturbed the nectophores are quite trans- 

 parent, a condition to which they return in about ten minutes after stimulation has ceased. The four 

 teeth may show this ' smoky ' appearance even when unstimulated. When the nectophores, some time 

 after detachment, become moribund they finally become ' smoky '. The change appears to take place 

 in the ectoderm, as Chun also observed. This species is one of the siphonophores most easy to keep in 

 confinement. A specimen with six or more nectophores, taken at Villefranche at 9 a.m. 19 May 1949, 

 was still alive and pulsating at 7.45 p.m. on 23 May, the room temperature being about 20 C. By 

 28 May it had given up swimming and had lost three nectophores but was still transparent and able 

 to turn 'smoky' when removed (in one piece) to a watch-glass. At 7.25 p.m. on that day I dropped 

 the specimen into Bouin fixative, whereupon one more nectophore became detached. Detached 

 nectophores can swim for days. 



The female gonophores were particularly active swimmers when detached, but as stated elsewhere 

 (p. 77) I was unable to fertilize and rear the eggs. 



A specimen of H. hippopus taken at Villefranche on 18 March bore fifty trichocercous cercariae 

 (with eyes), probably the larval stage (Cercaria setifera Monticelli) of the trematode Lepocreadium 

 album Stossich. 1 Some had made tubular tunnels into the jelly and lost their tails (metacercariae). 



1 See Dollfus, R.-Ph. (1925) and Palombi, A. (1937). 



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