CTENOPHORA „_ 



figure given of the latter by A. G. Mayer') is, as regards the colour, not in accordance with the 

 description of Agassiz. 



The Mediterranean sjjecies, Bolina hydatina Chun, is stated to differ from B. infundibubun, 

 besides in the less developed windings of the lobe-vessels and some other minor characters, in the remark- 

 able fact that the subventral vessels precede the subtentacular ones in the course of the de\elop- 

 ment from the young to the adult form, while in B. iiifnndibulum (alata) it is exactly the reverse 

 according to Agassiz. With full reason Chun points out (Dissogonie, p. 93) that "es ist im hoheu 

 Maasse auffallig, dass bei nahe verwandten Arten so bemerkenswerthe Differenzen in dem Gauge der 

 postembryonalen Entwicklung obwalten". Though the figures given by Agassiz show this verv 

 clearly, I think we may desire to see this statement verified by renewed researches. The fif. 8 

 especially does not appear to me very convincing, and I may call attention to the fact that in the 

 much more advanced stage represented in his fig. 12 the subtentacular vessels are represented 

 as ending at the sides of the lobes, not uniting in the middle, and not distinctly in advance of the 

 subventral vessels. Also the facts pointed out above in regard to his figures of young Mertriisia (wniii 

 make me hesitate in accepting as beyond doubt the statements and figures of the development of ^(^//;/«. 



There would, however, appear to exist another very conspicuous difference between the young 

 of B. infimdibiilinu and /lydatiiia. In the young specimen of ca. i""" diameter represented by Vogt 

 & Yung (Op. cit p. 175—176) in figs. 75 — 76 the tentacular vessel is represented issuing from one of the 

 . interradial vessels, not occupying the middle between the two interradial vessels. I have had occasion 

 to convince myself of the correctness of this observation (on a specimen of 1-5""" diameter). Judging 

 from Taf. IX, fig. 3 of Chun's memoir "Die Dissogonie", this would not appear to be the case in 

 B.hydatwa ; but no quite corresponding stage being figured by Chun, the existence of this difference 

 cannot be regarded as beyond doubt. 



If these differences in the development of B. liydatiiia and in/undibiiln/// prove to be sure facts, 

 there will, of course, be no doubt possible that they are really two different species. But until then 

 I cannot feel very convinced of the specific difference between the two forms. The length of the 

 auricles and of the costse are not reliable characters; I have observed a rather considerable variation 

 therein in B. infiiudibitluvi. The only difference of somewhat more value, which I can find between 

 hydatina and infundibuluvi is in the windings of the lobe-vessels. Judging from the fig. i, p. 82 of Chun's 

 memoir "Die Dissogonie", which represents a specimen of ca. 9""^ height, these windings are decidedly less 

 developed than in infiindibuliiin ; even though a not inconsiderable variation obtains in regard to the 

 development of the windings in B.infiindibuhuii , I have never observed them so little developed in the latter. 



The question about the specific value of Bolina Iiydafiiia must then be left undecided for the 

 present. Judging, however, from the fact shown above that the Mediterranean Plcurobrachia rhodopis 

 cannot be distinguished from PI. pileiis, and from the fact shown below, that the Mediterranean 

 Beroc ovata can, at most, be regarded as a variet}- of Bcroc citcuiiiis. it will probably be conceded that 

 the conclusion lies near at hand that also Bolina Itydatina. only found in the Mediterranean, is only a 



") A. G. Mayer. Some Medusae from the Tortugas, Florida. Bull. Mus Comp. Zool. Vol. 37. 1900. PI. 27. I'igs. 91-92. 

 Moser (Japanische Ctenoplioren, p. 53) supposes tliat the ros}' colour of the specimen figured by Mayer "luit der natur- 

 licheu Farbe uichts zu tun hat, da .\gassiz ausdriickUch die Farblosigkeit hen-orhebt und Mayer sonst wohl von einer 

 Identifikation beider Abstand genommen hatte". This point might well deserve an authentic explanation. 



