345^ 



CCELENTERATES 



the colony. Below these, again, comes a circle of extremely mobile tentacles, 

 which may perhaps be the tentacles of vanished bells. Among these tentacles are 

 hollow structures, open at the end, which are the feeding bells, now reduced to 

 sucking tubes, or stomachs, each of which endeavors to seize and digest for itself 

 whatever in the shape of 'food (chiefly small crustaceans) is brought to it by the 

 long capturing filaments and their branches, armed with stinging organs. The 

 colorless blood and nutritive fluid prepared by these two stomachs serve for 

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

 the axial tube previously 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, three, 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 Crelenterata 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 coloring. 



Physophora, WITH Two 

 ROWS OF SWIMMING BELLS. 

 (Natural size.) 



