^O MEDUSA. I. 



marginal vesicles. These have been described by Linko (1900, p. 4. Taf. II, Fig. 22 — 25). The marginal 

 vesicles are described as being very small and numerous, one inside each of the tentacles, situated in 

 the ectoderm on the subumbrellular side of the bell inside the circular vessel, just above the suppor- 

 ting lamella of the velum. The structure of the single vesicle could not be examined thoroughly 

 "wegen der schlechten Conservierung" (p. 5). Browne (1908) has tried to find these marginal vesicles, 

 but he found no trace of such organs; it seems reasonable, therefore, to suppose that the vesicles, 

 which Linko found is his, as he states himself, badly preserved material, have simply been due to 

 destruction of the tissues. We must, in any case, wait for new investigations of well-preserved material, 

 before the presence of marginal vesicles in this species can be stated. I myself have sectioned a part 

 of the bell margin of Staurophora without finding any vesicles, but, I admit, the material at my dis- 

 posal is not well suited for such examination. 



In the paper quoted above Linko mentions the structure of the ocelli, and he states that 

 within the same specimen we may find every transitional stage from a simple pigment-spot to a cup- 

 shaped eye with a lens. 



The most interesting feature in this species is the structure of the mouth. Brandt was of the 

 opinion that the animal had no mouth at all, but that the food was received through the lancet- 

 shaped "arms" in a manner corresponding to the facts in & Rhizostoina. Agassiz, on the other hand, 

 calls attention to the eminent extention of the mouth, the corners of the mouth being prolonged along 

 the four arms of the "cross". M. Sars (1863, p. 339) had a similar apprehension. When Haeckel 

 states as a feature characteristic for '■'■Stanrostouta arcticd\ that the outer half of the gonadial part is 

 closed, this must undoubtedly be due to a mutual gluening of the folded edges of this part of the 

 mouth; such gluening has been observed by several authors and is also seen in some of the specimens 

 examined by me. 



As the corners of the mouth extend as far outwards as the gonads, the latter may in some 

 way be said to have their position on the walls of the "stomach". Hartlaub (1897) takes this as an 

 argument of a near relationship to the Tiaridce. I am more inclined to think that the large extent 

 of the mouth in Staurophora is a secondary character, and Staurophora is hardly the genus among 

 the Laodiceidce which is nearest related to the Tiaridce. A clear picture of the manner in which the 

 mouth in Staurophora has to be understood, has been delivered by Browne (1907, p. 470): "If one 

 were to slit open along the middle the enlarged portions of each radial canal of Laodicea pulchra^ 

 and imagine the cut margins to be the margins of a mouth, then the position of the mouth, stomach, 

 and gonads would be similar to those of Staurophora. I think the mouth of Staurophora has arisen 

 by the outgrowth of a central mouth along the enlarged portions of the radial canals of a Laodice- 

 like medusa, and consequently those portions of the radial canals have been converted into a four- 

 rayed stomach. The gonads have not changed their position, but in Staurophora they have lengthened 

 slightly and meet in the centre of the cross". I quite agree with this apprehension. 



The hydroid generation is unknown; but quite young stages of the medusa have been obser- 

 ved by A. Agassiz (1862, p. 2, and 1865, p. 136) and Hartlaub (1897, p. 487), who have been able to 

 follow the development so far that the species might be identified with certainty. — The first develop- 

 mental stages of the egg have been observed by Wagner (1885, p. 80 — 81). — Hargitt (1904, p. 43) 



