PREFACE. 



IN this Part III., I have thought it best to place proportionately more of the 

 Supplementary Reports and less of the Pearl-oyster work than was the case in 

 Parts I. and II., for the following reasons : 



1. The Supplementary Reports here printed were ready and it might have been 

 unfair to the authors and unfortunate for Science if there had been avoidable delay in 

 publication by excluding any from this Part. 



2. Those sections of the Pearl-oyster work which were completed, or nearly so, are 

 of such a nature that the results can be communicated in -writing to the Authorities 

 in Ceylon, and a delay of a few months in making them known to the public seemed 

 comparatively unimportant. 



3. It seemed advisable, for obvious reasons, to have as much of the Pearl-oyster 

 work as possible placed together in Part IV., which will, I hope, be the final volume 

 of the series. This plan, moreover, presents the further advantage of allowing of 

 observations and conclusions to be drawn from the coming fishery in the spring 

 of 1905 probably the last which will be available for the purposes of this Report. 



Consequently the sections on Pearl-formation and Pearl-distribution and on the 

 different kinds of pearls and their natural classification have been postponed, and I 

 have inserted in this Part only (1) a discussion of the recent fishery (1904) based on 

 a report sent to me by Mr. HORNELL, (2) a statement as to the present condition and 

 future prospects of the beds of oysters on the Banks, based on Mr. HORNELL'S letters 

 and other documents, and (3) a further account of the internal Parasites of the Pearl 

 Oyster, by Mr. SHIPLEY and Mr. HORNELL, in which several new species of Cestode, 

 Trematode and Nematode worms are described and figured. 



The Supplementary Reports now issued deal with the Sponges, the Alcyoniidae 

 and the other Alcyonarians, the Opisthobranchiate Mollusca and the Ostracoda. 



The very considerable collection of Sponges (146 species, of which 77 were new to 

 science) has enabled Professor DENDY to make an extensive report, which is a notable 

 contribution to the taxonomy of the group. At least two of the Ceylon sponges 

 are of economic importance. The sponge of commerce, found in abundance at 

 Trincomalee, is of good form and consistence and might prove worth further cultivation; 

 and one of Professor DENDY'S new species, Cliona rnar;/<trififerce, is the boring sponge 



