3 20 COELENTERATA SCYPHOZOA 



Order II. Stauromedusae. 



This order contains several genera pro^'ided with an alioral 

 stalk which usually terminates in a sucker, bj means of which 

 the animal is temporarily fixed to some foreign oljject. There 

 can be little doubt that this sedentary habit is recently acquired, 

 and the wide range of the characteristic features of the order 

 may be accounted for as a series of adaptations to the change 

 from a free- swimming to a sedentary habit. 



It is difficult to give in a few words the characters of the 

 order, but the Stauromedusae differ from other Scypliozoa in the 

 absence or profound modification in structure and function of the 

 statorhabs. They are absent in Lucernaria and the Depastridae, 

 and very varialjle in number in Halidystus. 



The statorhab of Halidystus terminates in a spherical knob, 

 which is succeeded by a large annular pad or collar bearing a 

 number of glandular cells which secrete a sticky fluid. At the 

 base of the organ there is a rudimentary ocellus. The number 

 is very variable, and sometimes they are abnormal in character, 

 being " crowned with tentacles." There can be little doubt that 

 the principal function of these organs is not sensory but adhesive, 

 and hence they have received the names " colletocystophores " and 

 " marginal anchors," but they are undoubtetUy homologous with 

 the statorhabs of other Scyphozoa. 



The tentacles are short and numerous, and are frequently 

 mounted in groups on the summit of digitate outgrowths from 

 the margin of the umbrella. They are capitate, except in 

 Tessera, the terminal swelling containing a battery of nemato- 

 cysts. 



Very little is known concerning the life-history and develop- 

 ment of the Stauromedusae. 



Fam. 1. Lucernariidae. — ]VIarginal lobes digitate, bearing the 

 capitate tentacles in groups. Halidystus auricula is a common 

 form on the shores of the Channel Islands, at Plymouth, and 

 other localities on the British coast. It may be recognised by 

 the prominent statorhabs situated in the bays between the 

 digitate lobes of the margin of the umbrella. Each of the 

 marginal lobes bears from 15 to 20 capitate tentacles. It is 

 from 2 to o cm. in length. The genus occurs in shallow water 



