IUIIZOSTOM/E CAssmi'KA. c,:;7 



Tilesius, 1834, figured 4 species of Caisiofea and represented each of them as having 

 8 subgenital cavities. Relying upon the figures of Tilesius, L. Agassiz, 1862, separated the 

 genus Polyclonia, having but 4 subgenital cavities. Later researches have demonstrated 

 that all the known species of these medusae have normally hut 4 subgenital cavities, and 

 should therefore be placed in tin- s;enus Cassiopea. llaeckel, 1880, attempts to separate 

 Cassiopea from Polyclonia by calling medusas with 16 marginal sense-organs Casa 

 while those with 12 of these organs are called Polvcl'jniii. The nutnl>,r of marginal sense- 

 organs is, |IO\\I-\I.T, vciv variable, not onl}' among different species of these medusa: but also 

 among individuals of the same species, and therefore can not be used as a means of establish- 

 ing generic distinctions. 



The medusae of this genus are all inhabitants of warm oceans, and are found in gn.it< st 

 abundance in the tropical coral regions nf the Hast Indies and Red Sea. R. 1'. Bii>elo\\ finds 

 that (',. xamachana from the \\Yst Indies develops through the monodiscus strohili/ation 

 of a scyphostoma and the young ephyrae of this species and of 6'. fronJosa have a simple, 

 central, ^.-cornered mouth, thus recalling the adult condition in the Sein.eostonu.i-. from \\hich 

 forms the Rhi/ostom;e have evidently been derived. The rhopalia of the ephyra are derived 

 from the bases of each alternate tentacle of the scyphostoma, the other tentacles degenerating. 



1 he number of "species" of Cassiopea has been multiplied greatly, owm; to the remark- 

 able color-range and variability in other respects of these medusae. These color types appear 

 to be local, and the Cassiopea medusae of almost everv new region of the tropics are nearly 

 certain to be described as "new species" based on color peculiarities. It is therefore impos- 

 sible, at present, to classify the forms of Cassiopea with any degree of certainty. 



The blue and amber-green coloration of these medusae is due to the presence of com- 

 mensal plant organisms. Colasanti, 1886, describes the blue pigment matter as zoocyanin. 



Maas, 1 903, at tempts to separate the genus into two cohorts; one, consisting of (',. in, it, ;./. 

 C. tnertt-nsi var. ndrosia, polypotdes, xamachana, 'jinnt<i. and ornata var. Jigitata, distinguished 

 by its long, cylindrical, pinnately branched mouth-arms. The other group consists <>f ('.. 

 andromeda ami its varieties: C. deprcssa and (]. il<-pr?ssti var. />/./<;. This latter cohort has 

 irregularly branched, short, flat mouth-arms. An idea of the range in color-patteins uf these 

 medusas may be obtained from an inspection of plates 70 to 72 which exhibit photographs ot 

 a tew of the varieties of Cassiopea xamachana, all taken in the course ot ;ni hour tmni the 

 moat of Fort Jefferson, Tortugas, Florida. 



Stockard demonstrated that in ('.. xamachana the nearer the injury is made to the crnici 

 of the disk the more rapid the rate of regeneration. He also found that the more arms we 

 remove, the more does the central disk shrink dining the growth of the ICLK ru i .it inu arms, and 

 he thus finds that the regeneratm;; tissue absorbs nutriment at the expense ot the normal body 

 tissue as do cancerous tissues in then orovvth. 



Mayer finds that the rh\ thmical pulsation in ('.. \nm, i, li,ni,i is due to a nervous stimulus, 

 and this stimulus is caused by the presence of a slight excess ot sodium in the rhopalia over and 

 above the concentration ot this ion in the surrounding sea-water. This excess ot the sodium 



D 



ion is due to the constant tormation ot sodium oxalate in the sense-club, and this oxalate 

 precipitates the calcium chloride of the sea-water to form the calcium oxalate ci vst.ils of the 

 sense-club and sets free sodium chloride. 



R. P. Biuclow finds that the vesicles between the mouths of C. fronJosa serve to capture 

 prey and to thrust the food into the mouths. 



Cassiopea andromeda Eschscholtz. 



Medusa andromtda, FORSKAI , 1775, Dcscript. quc in It inert- Orient all Ol>M-rva\ it, Mauni.r, p. 107, tab 31 , ^ fii^n. 



Cassiopfa andromcdti, KSCHSCHOLTZ, iSii), S\ i . ,1< r Ai .ilrphcn, p. 43. TIMMIS, rX:<i. ' \1--n. N. C.. l->mc i >, 



p. 266, taf. 69, 70. Mits>-r.n\v\Ki, 1849, Curier's Rigne Animal DIunH, Zoopb., plate 51, tii;. I.- HMCWM. i" . 



Sjst. der Meduscn, p. 569. Kfiin. iSS8, Zool. Anzcigcr, BJ. 11, pp. 359, 389. Hjrtl.mli, ijo, /.li,i;. (.ihrt'inh'T. 



Abtll. Syst., H.I. l-J, p. 467, taf. n, fii;n. l-S. 

 Cassioftea jorskalta, PRON vi I.IM hi K. i Soq, Annal. du Mus. Hist. Nat., Paris, lomc 14, p. 356. 



Bell flat, shield-shaped, IOO to 120 mm. wide, 20 to 30 mm. high. 15 to 18, usually [6, 

 marginal sense-organs. A variable number of short, blunt lappets. In each p.nameie are I to 

 6, usually 3, velar flanked In 2 ocular lappets. 8 mouth-arms, wide. flat, and hardly as long as 



