THE CEYLON SPh^CIES OF UAULERPAS. 83 



precisely the genus Caulerpa as an example of a large genus with some 50 species that offer considerable 

 dissimilarities, but which nevertheless hve among identical external conditions. The differences between 

 the species are therefore not to be considered as due to adaptations, and in this he finds a support for 

 his theory of exclusively inner causes, " determinants," for the motley multitude of the organisms. 

 As a kind of confirmation of how this conception of the independence of external conditions among the 

 variable Caulerpas prevails in literature, we may mention what Madame Weber v. Bosse in a later 

 woi-k (" Etudes surlesAIgues del' ArchipelMalaisien," p. 128) has uttered in connection with the question 

 about the vegetative propagation of these plants : "La facilite avec laquelle les Caulerpes se multiplient 

 vegetativement et varient sous des influences qui echappent d notre perspicacite* est a nion sens indice 

 de plus qu'une reproduction sexuee ou par spores leur fait defaut." 



Oltmanns however rightly points out (in " Morphologic und Biologic der Algen," I., p. .312) that in 

 this matter we must, for the present, bide our time until the different species liave been studied in detail 

 in their natural localities, as well as the external factors that affect them there. 



That Caulerpas actually live under very different conditions can already be concluded from various 

 notices in the literature of the group. Thus, for instance, the only European species, C. prolifera, which 

 was almost exclusively the form that was the object of detailed investigations and which has therefore been 

 the physiological CaK/er^^o/iar/j/eVcVoiCf and has been made the type for the whole genus, is in the Medi- 

 terranean apparently a pronounced still-water form , which even if it can occur at tlie surface (0 • 5 metre 

 BEKTHOLD)yet seems to prefer deeper localities down to a depth of about 15 m.f That it lives under the 

 same conditions in the West Indies follows from Collins's note (in " The Algae of Jamaica," p. 245), that 

 it is not to be found at Jamaica except washed ashore. On the other hand, there are notices in literature 

 about other Caulei-jjas, which tell us that they live on rocks amongst corals or also in pools; of others, 

 again, that they live in sand and mud, often at no considerable depth (cf. for instance, the above 

 mentioned paper of Collins ; Reinbold.s ; the Marine Algae in " The Flora of Koh Chang"; A. Vickers' 

 " Contributions a la Flore algologique des Canaries " and " Liste des Algues marines de la Barbade," &c.). 



Therefore, to judge from certain statements in the literature, the Cauleipas do not live under 

 such quite identical external conditions as is commonly supposed. And that the Ceylon species of Caulerpa 

 occur to some extent under greatly different external conditions, and that this, in its turn corresponds 

 with evident differences in organization, I hope to show in the following pages. 



In examining whether, among a group of plants, the different forms or species really show ex- 

 amples of adaptations to their surroundings, or to employ a term first used by Detto, they are ecolo- 

 gisms (■' Okologismen "). we can proceed in different ways. Since, just as in the following case, direct 

 experiments were out of the question, the comparative method is the only one which analytic ecology 

 can adopt. We can, then, compare either widely different species, i.e., such as have different characters 

 of organization (" Organisations-Merkmale " to use Nageli v. Wettstein's expression), but which still 

 live amid similar surroundings, in order to examine whether, besides these characters, others of similar 

 kind (i.e. adaptations to the similai- surroundings) occur ; or, following Detto, examine whether they 

 may be examples of ecological convergence (Detto, loc. cit., p. 146). But we can also go to work in 

 another way; we may compare one species, which occurs very plentifully in one district in many forms 

 and amid different surroundings, in order to study the changes it undergoes in the different situations 

 and endeavour to find out whetlier tliese may be considered as adaptations to environment. 



Of the some 20 species of Caulerpa that I found in Ceylon, some are very rare and to be met 

 with in only few specimens ; others, it is true, have very Umited distribution, but show abundant local 

 occurrence ; some, finally, are very widely distributed, and occur in plentiful closely related 

 forms which are hard to distinguish. To the very rare species which are only found in scanty specimens 



* Italicized by the author of the present paper 



t Falkenbeeg- mentions C. prolifera in the Gulf of Naples at a depth of fr.->m 2 15m. Cf. also A. Vickers 

 Contribution a la ITlore algologique es Cdanaries," p. 30. 



