57S 



MEDUSA OF THE WORLD. 



Hadzi finds that some of the free-swimming planulae of Chrysaora are 4 or 5 times as large 

 as others. They swim with the broad end forward and soon settle upon ulva, etc., attaching 

 by means of their forward ends. The entoderm, which was previously a solid mass, then 

 hollows out and the larva becomes two-la\ ered, and the uppermost (the former posterior) end 

 becomes the widest. The mouth then breaks through, the oral pole flattens latcrallv, and 4 

 tentacles develop, 2 in the short and 2 at the ends ot the long diameter. The stomach-pouches 

 do not begin to form until after the mouth and 4 tentacles have developed. 



The view of Claus has received strong support from Hadzi who casts serious doubt upon 

 Geotte's interpretation that the oesophagus ot the scyphostoma is al\va\s composed of invag- 

 inated ectoderm. 



Hadzi, whose research upon Chrysaora appears to have been carefully studied, finds that 

 the oesophagus of the sc\phostoma is entodermal and that the mouth breaks through from the 

 inside, the entoderm thus taking the active share in its formation, and no invagination of ecto- 

 derm occurring. Indeed Hadzi finds that the cells lining the throat of the sc\phostoma resem- 

 ble ectodermal cells in having nematocyst capsules and glands, but they are nevertheless solely 

 of entodermal origin. From this it follows that the 4 primary stomach-pouches are also ento- 

 dermal, not 2 ectodermal and 2 entodermal as claimed by Goette. Hadzi finds also that the 4 

 intertentacular taeniolae are formed from 4 simple, longitudinal infoldings of the entoderm of 

 the stomach wall, the ectoderm taking no part in their formation. The primary stomach- 

 pouches are thus the passive result of the infoldings which form the taeniolae, not of an active 

 outgrowth of pouches as Goette believes. 



Hadzi's view appears to be the more reasonable, for if Goette were correct one half of the 

 gonads would be ectodermal and one half entodermal, whereas according to Hadzi they are all 

 entodermal; moreover, according to Goette, the mouth of the first eph3ra set free in strobili- 

 ■zation has its oesophagus lined with ectoderm, while those ephyrx which follow it have their 

 throats lined with entoderm, an anomalous condition, .'\ccording to Hadzi and Heric, how- 

 ever, all of the eph\rae have their throats lined with entoderm. 



Heric finds in the strobilization of the sc\phostoma of 

 Chrysaora that with the exception of the terminal ephyra all of 

 the mouth-tubes of the chain of ephyrae are formed from the 

 connecting tube which joins all of the ephyrae together. The 

 external wall of this connecting tube is ectodermal and its inner 

 wall entodermal. 4 perradial clefts develop in the side wall of 

 each tube near the upper end where it joins with theexumbrella of 

 the overlying ephyra. The lower edges of these clefts grow out- 

 ward and form the 4 lips of the eph\ra, while the 4 connections 

 are interradial and are in the radii of the ta;niola which consti- 

 tute their inner sides. 



The 4 subgenital cavities of the ephyra are new formations 

 and not derived from the 4 funnel-cavities of the scyphostoma. 

 The 4 interradial septa of the stomach-cavity of the eph\ra are, 

 however, derived from the taeniolae of the scyphostoma. These 

 soon disappear, and the central stomach of the medusa is a 

 simple lenticular space. 



The forms oi Chrysaora are so imperfectly separated one from 

 another that were it not for the fact that many minute distinc- 

 tions have been pointed out between them, I would greatly 

 prefer to consider them all to be one variable species, C. hysoscella. 

 However, we may possibly distinguish more or less vaguely: 



Fig. 365, — Diagrammatic section of 

 a strobilla of Chrysaora after 

 Heric, in .Arbeit. Zool. Inst. 

 Wicn. 



alif perradial cleft, am, beginning of 

 the lip. p, I, I, stages in the 

 growth of the throat-tube. 

 s rrtf septal muscle. Ectoderm 

 cross-hatched, entoderm plain, 

 intermediate lamella dotted. 



C. hysoscella= C mediterranea with its varieties hlossevillei and plocamia ( ?) 



of the Atlantic, Mediterranean, and South Pacific. 

 C. helvotaj with its varieties calliparea, and chinensis of the Pacific and 



Indian Oceans. 

 C. mtlanaiter with its variety gilberti of the North Pacific. 



1 believe that a study of the following synoptic table will 

 convince one that we have here only one species, the varieties of 

 which defy classification in terms of the Linnean system. 



