104 CEYLON MARINE BIOLOGICAL REPORTS. 



From what lias been said above it follows that the diflference in organization that prevails among 

 the predominating Caulerpa species in the north and in the south, and which depends on the difference 

 in the external conditions of hfe, can also be traced in such Caulerpa species as are rather to be considered 

 as being more accidental ingredients in the flora. Here, too, thinning, owing to external influences, 

 makes itself felt, so that, for instance, the rocks and reefs in the south harbour species that in their 

 ort^anization show themselves more fitted for these. 



It is remarkable that the north-east coast of Ceylon, as far as we know, has no Caulerpa that 

 is not known in other parts of the Island. It is striking, for instance, how at Trincomalee, where 

 the rocks seem to be excellent locaHties for algae, the marine flora is apparently scanty and, in richness 

 of species and luxuriance in general, very inferior to that on the rocks in the south-west. This fact 

 seems already to have made itself clear to Harvey, to judge by his disappointment at Trincomalee. 

 (See "Memoir of W. H. Harvey," London, 1869, p. 251). 



2. — The Distribution of the Ceylon Caulerpas in other places. 



Having dealt with the distribution of the Ceylon Caulerpas in Ceylon, we will investigate their 

 "eofraphical distribution elsewhere. But, first, we must remark that the following species are hitherto 

 only known from Ceylon : — 



C. imbricata j C. parvula 



C. dichotoma \ C. Fergusonii 



These, then, must^, for the present at least, be regarded as endemic species. 



Among the remainder we find that, of the species which make up the main mass of the Ceylon 

 Caulerpa vegetation, the majority are species with very wide distribution — from the Red Sea in the west 

 to the eastern islands in the Pacific, and also in the West Indies. Such species are — 

 C. clavifera C. Chemnitzia 



C. uvifera C. peltata 



C. sertularioides 

 C. nummularia is not reported from a more western point than Ceylon, and seems to have its 

 main distribution in the Indian Archipelago and tropical Australia. In this connection it must, of 

 course, be borne in mind that such statements about distribution must be taken with some reserve as far 

 as the definition of the species is concerned, as different authors have different interpretations for the 

 various species. Dealing with the distribution of the species, one has therefore always to reckon with 

 the wider sense of the name in question. The restricted species and forms are, of course, much more 

 limited in their distribution. 



Of the Caulerpa-sTpecies that are comparatively rare in Ceylon, the two following have also the 

 same extended distribution (Red Sea, Pacific, West Indies) : C. crassi folia and C. Freycinetii. 



On the other hand, there are several of the rarer species for which Ceylon and the peninsula of 

 India form the western limit of their distribution, as far as we know. Such are : — 

 C verticillata \ C. Lessonii 



C. taxifolia i C. corynepJiora 



C. cupressoides \ C. sedoides 



and possibly C. longistipitata. 

 The last-named is, be it noted, only found beyond Ceylon in the Gulf of Siam, and has thus its 

 west limit in Ceylon ; but, on the other hand, the closely related lentillifera has a still more pronounced 

 west distribution, since it occurs in the western parts of the Indian Ocean (Madagascar). 



While, comparatively speaking, .so many species have their western limit in Ceylon, i.e., they them- 

 selves have a more easterly centre of distribution, it is very striking that Ceylon is not the east limit for 

 hardly more than one species, viz., C. scalpelliformis , which together with closely allied forms occurs 

 from tlie Red Sea to Ceylon in the nortlx and has also a wide distribution on especially the west and 



