482 



CCELENTERATES. 



for the nourishment of the whole colony, and are carried to the various parts 

 through the axial tube above mentioned. In the illustration, which has been 

 chosen on account of its comparative simplicity, no reproductive or egg-bearing 

 bells are shown. When present in the Physophora, these appear like clusters of 

 grapes ; in other genera they are capsules ; in others, again, they may be actual 



swimming -bells, which become detached, and lead an 

 independent life. This fact is of importance in helping 

 us to understand this complicated organism. It shows 

 that the Physophora is not a single animal, but a stock 

 or colony. Of this there is evidence in the rowing-bells, 

 as well as in the two, ihree, four, or more sucking-tubes, 

 with distinct mouths and stomachs. And, lastly, we have 

 the reproduction brought about, in some cases, by detached 

 jellyfish-like individuals. All the parts of the organism 

 form a whole in a physiological sense ; they belong to 

 one life, and many are so modified as no longer to appear 

 as individuals. But, on the other hand, some of them 

 are fairly independent, and, when they take the form of 

 medusae, they are so highly developed that their individu- 

 ality is at once manifest. We must, therefore, regard 

 a Siphonophore as a colony of highly - modified in- 

 dividuals, which owing to the fact that these individuals 

 differ greatly in form and function constitute what is 

 termed a " polymorphous colony." 



One of the most beautiful and most dangerous of 

 the Coelenterata belongs to the Siphonophora. This is 

 the so-called Portuguese man-of-war (Physalia), several 

 species of which are found in the southern seas. The 

 air-bladder at the top of the stem is a large, oval vesicle, 

 which projects above the surface, lying horizontally on 

 the water. It is drawn out into two points at opposite 

 poles. A comb runs lengthwise and somewhat slantingly 

 along the top of it. From its lower side, nutritive polyps, 

 feelers on which the genital products develop, and very 

 long tentacles hang down side by side below the surface 

 of the water. Another strikingly beautiful species found 

 in the Mediterranean is P. pelagica. Lesson writes that 

 these creatures " shimmer with the most splendid colouring. 

 The air-bladder and its comb look like molten silver, adorned with light blue, 

 violet, and purple. The small thickenings on the keel of the comb are of a vivid 

 carmine, while the appendages are of a wonderful, delicate, ultramarine blue." 

 The English name is happy, as it indicates the latitude in which the traveller 

 from Europe first meets with it, its ship-like appearance on the surface of the 

 water, where it uses its comb as a sail to catch the wind, and its ample provision 

 of weapons. The tentacles of the Physalia are stiff with batteries of stinging- 

 capsules, and those who are careless enough to touch them will repent. Meyen 



Physophora, WITH TWO ROWS 

 OF SWIMMING BELLS (nat. size). 



