IO4 



ASSOCIATION OF ORGANISMS THE WEB OF LIFE 



are transformed into fishing-lines that catch food, and at the same 

 time are so well provided with stinging-cells as to effectively keep 

 off enemies. There are also digestive individuals, which devour 

 and digest the animals caught by the fishing-lines. Some mem- 

 bers are reduced to tentacles, ministering to the sense of touch 

 (and possibly smell); others again are in the form of protective 



plates, covering and sheltering adjacent in- 

 dividuals. And the/e are also egg-produc- 

 ing members of the colony which may be 

 liberated as little medusae, thus promoting 

 dispersal. In different species there are 

 considerable variations in detail, and the 

 actual arrangements in one case (Stephalia 

 corona) are shown 

 in fig. 1093. 



COLONIAL MOSS- 

 POLYPES (POLYZOA). 

 - With a single 

 exception the mem- 

 bers of this group 

 produce colonies by 

 budding, after the 

 fashion of Hydroid 



Fig. 1092. Diagram of various in- 

 dividuals in a colony of Compound 

 Jelly -Fish (Siphonophora\ central 

 cavity of colony indicated in black. 

 Jl, Float ; s, swimming-bell ; d, d, 

 digestive individuals;./!/., branched 

 fishing-line; pr, protective indivi- 

 dual ; p, p, p, various forms of pro- 

 pagative individual; t, tentacle. 



for 



are 



Zoophytes, 

 which they 

 sometimes mis- 

 taken, though in 



tn.d. 



Fig. 1093. A Compound Jelly- Fish 

 (Stephalia corona], reduced, fl, Float; 

 s, swimming-bell ; g, gas-conducting indi- 

 vidual; d, small digestive individual; m.d., 

 large central digestive individual; t, ten- 

 i i i tacle; p, group of small propagative in- 



reality much higher dividual* 



j o 



in the scale. Some 

 of the members of such a colony may be greatly specialized for 

 various purposes (fig. 1094), e.g. they may be modified into rounded 

 receptacles (ovicells) in which the eggs develop till the time of 

 hatching. In certain species there are bird's-head individuals, 

 which execute vigorous snapping movements, the object of which 

 is extremely doubtful. Cleanliness is possibly promoted, or per- 

 haps the attacks of small parasitic forms may thus be warded off. 

 It has also been noticed that the powerful jaws often succeed in 

 catching little worms, crustaceans, &c., apparently holding them 

 tenaciously till they die and decompose. The suggestion has been 

 made that the decayed fragments of these victims are carried by 



