252 THE VOYAGE OF H.M.S. CHALLENGER. 



January 15, 1867, in the Canary Island Lanzerote. Quietly expanded on the surface of 

 the water, it had the form drawn in fig. 1 , but this lasted only a few minutes. Most of 

 the time the animal was in continuous very rapid motion, quite unusual among the 

 Physonectse. It swam through all parts of the vessel very quickly, without touching 

 its sides, with rapidly succeeding contractions of the nectophores. The siphosome was in 

 the swimming animal strongly contracted, the corona of bracts closed, and the strong 

 bilateral compression of the corm, with two sharp opposite keels in the sagittal plane, 

 seemed to be excellently adapted for the rapid swimming motion. 



Nectalia loligo, n. sp. (PL XIII.). 



Habitat. — North Atlantic, Canary Islands, Lanzerote, January 15, 1867 (Haeckel). ■ 



Nectosome (figs. 1-8). — The swimming apparatus is composed of a rather long tubular 

 trunk, which bears at the apex a pyriform pneumatophore, and beyond it a double series 

 of opposite nectophores in four pairs obliquely. The length of the nectosome is 20 mm. 

 to 25 mm., and about equals that of the largest bracts of the siphosome. There was a 

 group of buds of nectophores at the base of the pneumatophore, marking the blastocrene 

 of the nectosome, or its point of vegetation. 



Pneumatophore (figs. 1, 2, 2>,p>, 4). — The float at the apex of the nectosome was in the 

 living animal pyriform, with a red apex and an oblongish pneumatocyst filling up its 

 upper half (fig. l,pf). Preserved in alcohol (fig. 4) it appeared under an altered form, 

 subcylindrical, with two annular constrictions of the included pneumatocyst (f>f)- The 

 pneumatosaccus surrounding the latter is rather wide, and connected with the pneu- 

 matocodon by four cruciate radial septa or vertical mesenteria {pi'). The pericystic 

 cavity of the pneumatophore, therefore, is divided into four radial pouches, (ps). 



Nectophores (figs. 1, n, 3, in, buds, fig. 5, a young nectophore, figs. 6-8, adult necto- 

 phores, 6, dorsal view, 7, basal view, 8, lateral view from the left side). — The umbrella of 

 the nectophores is strongly compressed in the direction of the sagittal axis, which is 

 3 mm. or 4 mm. long, half as great as the frontal and the principal axes (both 6 to 

 8 mm. in length). The truncate basis, with the ostium of the nectosac, is directed 

 obliquely outwards, whilst the opposite apex has a deep square excision. The two lateral 

 horns or wings, which are separated by the latter, are square in frontal view (fig. 6), 

 triangular in lateral view (figs. 1, 8), of a three-sided prismatic form, and embrace the 

 trunk of the nectosome, so fitting in the interval between the two opposite nectophores 

 (superior and inferior) that they fill up the interval between them. The superior or 

 dorsal face of the umbrella is slightly convex, with a median sagittal groove, and fitting 

 exactly into the concave lower or ventral face of the next superior nectophore. In the 

 median line of the ventral groove arises a sagittal ridge, which bears a short pedicle 



