THE LIFE OP THE SLIGHTLY COMPLEX ANIMALS 47 



dusa individuals, whose 

 business it is to be the 

 locomotive organs for the 

 colony. These medusae 

 are without tentacles, and 

 take no food and produce 

 no young. They have 

 given up the power of 

 performing these other 

 life processes, and devote 

 themselves wholly to the 

 business of locomotion. 

 From the lower end of the 

 central stem rises a host of 

 structures, among which 

 several distinct kinds are 

 readily perceived. One 

 kind is composed of a pear- 

 shaped hollow body open 

 at its free end, and bear- 

 ing a long tentacle which 

 is furnished with numer- 

 ous groups of stinging 

 cells. These are the polyp 

 individuals whose especial 

 business it is to capture 

 and sting prey and to eat 

 it. These individuals are 

 the food -getters for the 

 colony. Scattered among 

 these stinging, feeding 

 polyps, are numerous 

 smaller individuals with 

 oval, closed body, each 

 bearing a long, slender 

 thread. These threads 



FIG. 25. A colonial jelly-fish, Physophora 

 (after HAECKEL). At the top is the float 

 polyp, around its stem the swimming 

 medusae, and below are the feeding, feel- 

 ing, protecting, and reproducing polyps 

 and medusaj. 



