ACALEPH.E. Ill 



Note. If the figures in FORSKAL, Tab. xxvi. fig. k^, k^ k$, belong to 

 a young Velella, as appears from the explanation of the plate, this genus 

 must be suppressed ; which is BLAINVILLE'S opinion. 



Porpita LAM. The Lamina cartilaginous (?), circular, marked 

 with concentric stride decussated radially. Marginal tentacles 

 appendiculate. 



Sp. Porpita mediterranea ESCHSCH., Porp. Forskalii, DE HAAN, Hoi. denu- 

 data FORSK. Icon. Rer. nat. Tab. xxvi. fig. L., in the Mediterranean ; 

 Porp. umbella ESCHSCH., Porp. gigantea PE'RON, Voy. aux terres austr. 

 PI. xxxi. fig. 6, in the Tropical Seas ; Porp. chrysocoma LESS., GUERIN 

 Iconogr., Zoophytes, PL xvin. f. 2. (Medusa Porpita L. is merely the 

 cartilaginous disc of some species of this genus.) 



Family II. Physsophoridce (Hydrostatica Cuv.) Body sus- 

 pended in the water by means of a swim-bladder or of receptacles 

 filled with air. 



Bladder-bearers. The opinion that these animals are able to 

 expel the air from the air-bladder at will was rendered doubtful, as 

 a general rule, by OLFEKS, who could find no opening in the large 

 bladder of Physalia. [Subsequent observations however have deter- 

 mined that Physalia is the only one of the Physsophoridce whose 

 bladder does really communicate with the external air. But, though 

 there be no such communication in the rest, LEUCKART states that 

 in many of them (and he believes it to be true of all) the air may 

 be readily caused to pass from the cavity of the bladder into that of 

 the common stem, by the expansion of the upper extremity of which 

 the air-bladder is in all cases surrounded. 



a) with short stem or axis without swimming bells. 



Physalia LAM. Swimming bladder very large, crested above, 

 with an aperture at one extremity : the whole of the common stem 

 expanded so as to form a receptacle for it : from the inferior surface 

 of the expanded stem the polyps are suspended together with 

 feelers and prehensile organs, of different thickness and of great 

 length.] 



/Sea-bladder. The colony swims constantly on the surface of the 

 sea, and for that purpose makes use of the crest on the top of the 

 bladder as a sail. Hence its name, het bezaantje, the Portuguese 

 man of war, la petite galere, &c. If in the nomenclature we ought 

 strictly to hold to priority, then this genus ought to be named 



