THE ANIMAL LIFE OF THE CROEP. 481 



seitihliiiu' seM-iiKisscs tliat it is with (lifliciill y that the uiit i-a iiicd ohscrv.-r is 

 convinced that they arc really animal ('(donies. Sonic of the <;cncra ■'•' ai-e 

 ■well-known animals and occasionally limned in 'general reference books. The 

 Hawaiian species in every case aie i-arer foims Ihat can oidy he recog-nized bv 

 experts when aided by elaborate descriptions. 



In this connection mention slionid be made of certain colonial hydi-oids"*" 

 that secret masses of carbonate of lime ont of which the aninnd |)fot iMuh's like 

 a coral polyp. They ai-e usnally jnnk oi' oran.u'e-colored. and an- often called 

 corals. Several species are fonnd very ])lentiful!y on onr coral reefs. On 

 close examination it will be seen that tlu'y differ in strndui'e from the true 

 corals. The solid-looking masses with lobed processes, or bosses, are the most 

 common, -^1 though fine branching examples-'- also occnr. In both fjuiiiiies the 

 whole surface can be seen, with the aid of a lens, t;) be coxci'cd with small 

 pore-like openings. If a vertical section is exaiuined. indistinct layei's can be 

 seen running parallel with the outer surface. Only the surface is alive, the 

 inner mass being composed of the dead skeletons. Thus these animals secrete 

 lime aiul build up a coral-like skeleton in much the same way as do the ti'ne 

 corals, which are f)olyp colonies and quite different in their oi-ganizatioii, 

 though secreting similar masses of lime. 



Zor»logists often cite this peculiai' fact as an example of "con\-ergence.' ' 

 meaning thereby that two animals of diffei'cnt ty[)cs have becoim' adapted to 

 similar conditions of life and come to superficially resemble each other. Other 

 animals, as whales and fishes, bii-ds and bats, show similar evidence of con- 

 vergence. Indeed, it has not been uncommon foi- naturalists to place totally 

 different animals in the same grou]) on account of theii' I'csemblance. The 

 Hawaiian HijdrocoraUiuce have not been full\- studied as yet. and there appi^ars 

 to be no list of even the common species. 



The Portuguese IMan-op^-AVau. 



Sea-bathers occasionally make the acquaintance of the I'ortugut'st' man- 

 of-war,^-^ which is perhaps the best known member of a third family ^^ of the 

 jellyfish tribe. It floats, l)y means of an air sack, on the surface of \ho sea. 

 Its stinging ])ower is tremendous, producine ;i maddening, scald'ng pain which 

 lasts for hours. As the stinging tentacles are loni;- and 1 h.read-like and lloat 

 ont loosely in the \vat<'r. the beantil'nl "bine bottles" are Ihines that can be 

 more safely admii-ed at a considerable distance. On the windward shoi-e of all 

 the islands they are often stranded by thonsands by the ebbine tide, where they 

 dry down to a mere bubble in a few honrs. 



Ska .Money. 



Another common form ^''' is a llat coin-sha|>ed disk with line radiatinir 

 white lines. About the edge nvc innumerable line tent;udes. The animal. 



^^ Serfiilririd. Cam imii iihi riii :ni(l I'linii kUu-'ui. *<> JJiidrororiilHiKV. " Milh'iiDi-iihr. 



*^ Stiilasti'fidiv. *•' I'hi/siiliii III ririihiii. *^ Siphniiophdnv. *'• Parintn imrifira. 



