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BULLETIN: MUSEUM OF COMPARATIVE ZOOLOGY. 
Ill. SIPHONOPHORAE. 
Porpita lutkeana Branpr. 
Brandt, 1825, Mem. Acad. Imp. St. Petersbourg Sci. nat. ser. 6, tome IV. 
Plate 7, Figs. 24, 25, 26. 
It is with considerable hesitation that I refer our specimens of this genus to 
the Porpita lutkeana of Brandt, which seems, however, to fit them better than 
any other described species of Porpita. The Pacific and Indian forms of the 
genus have always been in confusion, owing to the fact that most of the early 
descriptions are altogether insufficient for identification. Haeckel (Siphono- 
phorae of the “ Challenger ” Expedition) recognizes, besides the well-known At- 
lantic forms, Porpita lutkeana Brandt, to which he gives the synonym, Porpita 
indica (see ibid.); Porpita pacifica Lesson = Porpita gigantea Péron et Lesu- 
eur; Porpita australis Haeckel (System der Siphonophoren); and Porpita 
fungia Haeckel (Siphonophorae of the “ Challenger ” Exped.). 
Porpita lutkeana agrees in general with our specimens, although Brandt’s 
description is so meagre that an accurate determination is very difficult. 
The disc, in the largest specimen, measured forty-five mm. in diameter and 
five mm. in thickness. The upper, external surface of the exumbrella bears 
a series of minute knobs and corrugations, making it rough to the touch. The 
central chamber and the eight primary radial chambers are large, and com- 
municate with the exterior by prominent stigmata. Over the rest of the exum- 
brella the stigmata are very irregularly arranged. There are thirty-two circular 
partitions, at nearly equal distances, dividing the pneumatocyst into as many 
circular chambers, which are in communication with each other through 
openings in the circular partitions. The floor of the float cavity is thrown into 
a series of deep radial furrows and ridges, which interlock with the underlying 
ridges and furrows of the liver. These corrugations arise at the centre as eight 
folds, which by branching come to number about sixty. In addition to these 
and alternating with them, a series of shorter folds, arising at the periphery, 
runs centripetal for a short distance between the original centrifugal ridges, 
making the total number at the margin about one hundred and twenty. 
The liver is of considerable thickness, completely filling the space between 
the bottom of the float cavity and the lower surface of the disk, where it com- 
municates with the bases of the reproductive polypites. 
There are about two hundred tentacles, arranged in about four or five con- 
centric rows, instead of the nine rows described by Brandt. When fully ~ 
extended they are about as long as the diameter of the disc. Each tentacle 
bears three distinct rows of knobs, in the manner typical of the genus. At the 
tip of the tentacle there is a cluster of four, and this number appears invari- 
able. In each row there are about ten knobs. 
The central sterile polypite is large, with smooth walls, and very distensible. 
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