Allies of Medusse 41 



branched forests like moss, on the surface of stones 

 and shells. A common habit gave this set of creatures 

 their common name; but, although they were grouped 

 together, there was no greater affinity among them 

 than there is racial affinity among people who clothe 

 themselves for an evening party in the same conven- 

 tional dress. Huxley examined a large number of 

 these, and picked out from them two great families of 

 polyps, the Hydroid and Sertularian polyps, which 

 each consist of colonies of creatures very much like 

 the little fresh-water h^alra. He shewed that the 

 tubular body of these and the ring of tentacles sur- 

 rounding the mouth were composed of the same two 

 foundation-membranes of which all the organs of 

 Medusae are composed. He found in them the poisoned 

 arrows or thread-cells of the Medusae, and the same ex- 

 ternal position of the reproductive organs. And, lastly, 

 he separated from all other creatures, and a.ssociated 

 with his new group, some of the strangest and most 

 beautiful animals of the tropic seas, known to science 

 as the Physophoridae and the Diphyidae. The best- 

 known of these is the " Portuguese man-of-war," the 

 body of which consists of a large pear-shaped vesicle 

 which floats on the water like a bladder. From the 

 lower part of this depend into the water large and 

 small nutritive branches, each ending in a mouth 

 surrounded by a circle of waving tentacles armed with 

 batteries of thread-cells, while another set of hanging 

 protrusions bear the grape-like reproductive organs. 

 On the upper surface of the bladder is fixed a purple 

 sail of the most brilliant colour, b}' which the floating 

 creature is blown through the water. When the 

 weather is rough, the bladder empties, and the creat- 

 ure sinks down into the quiet water below the waves. 



