ACALEPHA5. 
237 
curious observations of M. Vogt. Fig. 95 is a representation 
" f Physophora hydrostatiaa, after M. Vogt's memoir. We see that 
animal is composed of a slender vertical axis, terminating in an 
aer >al bladder, carrying laterally certain vesicles, known as swimming- 
^alls, which terminate in a bundle of whitish slender threads. 
File aerial bladder is brilliant and silvery, punctured with red spots. 
Te swimming-bladders are encased in a transparent and somewhat 
Ca i'tilagi nous capsule, which is continued into the common median 
trnil k, the latter being rose-coloured, hollow, and very contractile ; in 
s lrort, it presents very delicate muscular fibres, which expand them- 
^ v es on the external fan of the capsule, and is closed on all 
sides. 
The swimming-bladders are of a glass-like transparency, and of a 
riXl i compact tissue. They are attached obliquely and alternately upon 
a common axis, presenting an exterior curvature, a round opening, 
Wished with a fine, muscular, and very contractile limb, and ar- 
j^ged like the iris of the eye. Their power of resistance is increased 
i' certain horny hollow threads, which are in direct communication 
'! lth the cavity of the vertical trunk, and have their origin in a common 
^C'dar canal. 
. “The animal,” says Vogt, “is enabled to guide itself in any diree- 
l0ri Ty means of the swimming apparatus or air-hags. These, on 
^ )enil ig, are filled with water, which is again ejected in the contractile 
° Ve ment, for them movements may he compared to that of the um- 
| tella of the Medusa 1 . It is the violent expulsion of this liquid which 
^dileg the animal to advance diagonally tlmough the water, a kind 
r Motion which is the consequence of its organization ; for where both 
" 8 air-hags are w T orking in the direction of the axis of the trunk, 
c or ganism will incline to the side which works most, hut always in 
’ a manner that the aerial vesicle will he home forward.” 
it !■ f°wer parts the trunk expands, becomes flat, and winds 
jj‘ 6 . I 11 a spiral. It is hollow, and encloses a transparent viscous 
th^’ w Tich very small granules are observed, which, appear to he 
0 j! G lesi ilt of digestion. This disk is attached to three different sorts 
a PPendages; we shall first address ourselves to the tentacles. 
•the 
c J_Jle se form a crown or bundle of vermiform appendages, of a reddish 
" ~ver an inch in length, and which are kept continually in 
these are formed of a glass-like cartilaginous substance; 
our, 
don 
