1881.] The Siphonophores. — 777 
There remains among the Physophoridz, closely resembling in 
general outline the type Agalma, several genera which should be 
mentioned in this place. One of these is so well marked that it 
can be easily distinguished at a glance, and in one important par- 
ticular is different from all the other Physophores. It will be 
remembered in my account of the arrangement of the swimming- 
bells of Agalma, published in the first article of this series, that I 
described these organs as arranged ia two rows, the lines of the 
two series apparently opposite on the axis. As is true also of 
other genera, where nectocalyces occur, this appearance of being 
placed in two rows on different sides of the stem, is brought about 
by a twisting of the axis itself, and not by a formation of the 
bells on opposite sides. If the axis of Agalma has its fibers 
straightened, all the covering-scales, swimming-bells and the like, 
would be found one above the other in a line: Consequently the 
biserial arrangement of the swimming-bells is wholly distinct 
from their place of apparent origin on the axis, but dependent 
upon the twisting of the axis itself. In the genus Stephanomia,' 
instead of the section of the stem between the position of origin 
of two nectocalyces taking a turn through an angle of 180°, thus 
bringing the nectocalyces into two series; the stem between two 
adjoining swimming-bells is twisted at a smaller angle, even one 
less than a right angle, so that the openings of the bell cavity 
face on all sides. There still remains a serial arrangement of the 
bells, but in Stephanomia it is no longer biserial as in Agalma, 
but multiserial with the bells opening in all directions in a plane 
at right angles to the axis. The polyp-stem in this beautiful ge- 
nus resembles that of an Agalma, but the feeding-polyps are 
mounted upon long peduncles, so that the tentacles seem to origi- 
nate on the polypites midway between the stem and the mouth. 
Covering-scales of peculiar outline are also present, as well as 
“tasters,” and male and female sexual-bells. In all of these 
structures, the genus is very characteristic, and if its whole organ- 
ization be considered, is probably the highest member of the fam- 
ily. The arrangement of the swimming-bells, opening as they 
apparently do on all sides of the stem, make it possible for the 
Whole colony to move rapidly through the water, and nothing can 
€xcel the grace with which these animals make their way through 
This genus was commonly called Foskalia by European naturalists; Stephanomia 
has a prior claim as its true name. 
VOL, XV.—-No, xX. 54 
