1880. | The Siphonephores. 621 
The different appendages or members all arise from one side of 
this axis; this side has been called a ventral line. The fact that 
they appear to take their origin on all. sides is brought about by 
a twisting of the stem itself There are two regions to be distin- 
guished in the stem, which are known as the necto-stem and the 
polyp-stem, The former is known by appendages which act as 
means of propulsion, the latter by the polypites or feeding polyps. 
Agalma is said to be polymorphic because it bears on the stem 
individuals which assume different forms according to their 
functions. These individuals are as follows (Fig. 1, letters as 
elow): 
I. Appended to ~ necto-stem : 
e floa 
he necto- cuiva or swimming bells. 
II. Appéeded to the polyp-stem 
c. The covering scales or PEA 
d. Polypites or feeding polyps, from which hang 
e. Tentacles and tentacular knobs. 
J- Tasters. 
g. Sexual bells of two kinds, male a female. 
Those who believe with Leuckart that every bud on the animal 
is an individual, must regard the tentacular knobs also as separate 
individuals. The float, necto-calyx and covering scale are of 
jelly-like consistency, and are modified “medusa bells.” The 
polypites and tasters are modified probosces, and the sexual bells 
are combinations of both. The last are the most perfect mem- 
bers of the whole colony. The tentacles are organs and not 
individuals, although so looked upon by many naturalists. The 
same remark also applies to the tentacular knobs. The first 
Structure to be noticed is a little sac filled with air, which is called 
the float. 
The Float—The only PE to the stem which is not 
duplicated except in monstrosities is the air-bladder or float. In 
Agalma it is very small and seems hardly large enough to buoy 
the animal up. It is supposed to keep the colony upright as it 
swims in the water. Many naturalists regard the float as the 
enlarged end of the axis in which, from its upper walls, hangs a 
sac filled with air, Itis supposed by them that the extremity of 
the stem has been infolded like the finger of a glove when 
reversed, and that the edges of the stem at the position of infold- 
ing had approached so as to leave a small opening leading from 
the reëntering part into the surrounding water. This opening can 
