No. IV.— MEDUSAE FKOM THE INDIAN OCEAN. 



(Collected by Prof. Stanley Gardiner, in H.M.S. " Sealark," in 1905.) 



By Edward T. Browne, M.A., F.L.S. 



Plate 39. 



Read 17th June, 1915. 



INTRODUCTION. 



The collection of Medusae, made by Prof. Stanley Gardiner during the voyage of 

 H.M.S. " Sealark " in the Indian Ocean, between Chagos, Mauritius and Seychelles, in 

 1905, was sent to me for examination. I heartily thank Prof Gardiner for allowing 

 me the privilege of writing this report upon the specimens, and must also express to 

 him my regret for the delay over the work. 



The chief interest in the collection centres in the geographical distribution of species 

 as this part of the Indian Ocean had scarcely been explored for medusae. It should be 

 borne in mind that the collecting of medusae was only a subsidiary part of the expedition's 

 work. Nevertheless Prof Gardiner was able to collect not less than thirty-five different 

 genera, but none proved to be new to Science. The species were slightly more numerous 

 than the genera, three new ones have received names, and others could have been added 

 if the specimens had been in better condition. 



The Anthomedusse show a much better list of genera and species than in the 

 previous collections from the Maldives and Ceylon. The poor list of species belonging 

 to the LeptomedusEe is partly due to my failure to identify the specimens. There are 

 always a certain number of bad specimens in every collection, and it so happened that the 

 Leptomedusse got more than their fair share of these. 



The Anthomedusee and- Leptomedusse are associated with the littoral fauna and are 

 rarely found far from land or shallow water. Many of their genera are known to be 

 connected with hydroids, so that their geographical distribution depends upon their 

 hydroids finding a suitable habitat. Some are widely distributed, others have a very 

 limited range. It is certainly strange that some of the commonest species have so far 

 evaded the search for their hydroids and leave us still without a clue, but it is difficult to 

 presume that some have no alternation of generations. 



It is unfortunate that systematists on medusae still hold divergent views over the 

 question of species, but nevertheless progress is slowly being made. There has been 

 a good advance since the day that saw the appearance of Haeckel's monograph which 

 was by no means a success, except from an artistic point of view. 



SECOND SERIES— ZOOLOGY, VOL. XVIL 22 



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