fact that these algae are much harassed by lower animals or on the whole much encumbered 

 with different extraneous objects, and, therefore, have to carry on a hard struggle for existence. 

 Consequently these algae must be supposed - - at any rate to some degree — ■ to be more 

 checked than others in their distribution over larger areas. It is possiblé that also other efficients 

 make their play contributing to impede the distribution of some species. 



However, it must be considered as proved that some of the forms in question are 

 distributed over great parts of the Pacific and the Indic Oceans, probably also of the Atlantic. 

 But the limits of this distribution are rather uncertain, and above all it is as yet dimcult to 

 realize, whether any species occurring in the Malay or Pacific Archipelagoes concerns the 

 Pacific or Atlantic coasts of America. This seems, however, to be the case with e. g. Lithophyllum 

 oncodes, which probably also occurs both on the southern coast of California and in the West 

 Indies. On the other hand, Goniolithon Reinboldi, apparently widely distributed in the Indian 

 Ocean and common in the Malay Archipelago, has up to the present not been met with 

 farther to the east, than at the Sandwich Islands in the North Pacific. In addition, a great 

 deal may be said in favour of the notion that among the species of calcareous algae hitherto 

 described from different areas, there are some identical ones, or one is likely to be considered 

 only as a somewhat varying form of the other. Thus Lithophyllum pallescens Fosl. ') (including 

 L. californiense Heydr.) from the Gulf of California is so closely allied to Lithophyllum 

 Okamurai, classified in this paper, from the Pacific coast of Japan and several places in the 

 Malay Archipelago, that the limit is hardry to be drawn. This is also the case with Lithophyllum 

 decipiens, from the coast of South America 2 ) and apparently also of the West Indies, in relation 

 to Lithophyllum Ycurfoi, mentioned below, from Japan and some other places in the Pacific. 



For the present, I therefore, find no reason to classify the forms of Lithotha-mnion 

 eruöescens from the East-Indian Archipelago as an independent species, the less so, as it has 

 been impossible to me to draw any certain line. On the other hand it is certainly to be 

 observed that the direction of variation within a species is hardly to be stated only from some 

 few specimens, as is the case with f. americana of the said species. In fact there are independent 

 species both of the genus Lithotha-mnion and Lithophyllum which are so closely allied to each 

 other that their mutual relations only can be fully characterized on the ground of a fairly 

 considerable material from several places. On the other hand there are instances where, judging 

 from a scanty material, plants were considered as fairly well defined species which afterwards 

 a larger collection have shown to be but varying forms, parly even but local forms of one 

 and the same species. It is further to be observed that the only reproductive organs hitherto 

 known of L. erttöescens are sporangia. The other reproductions organs are unknown, and it 

 will probably be the discovery of these organs that will decide the delimitation of the species. 



By comparing the specimens of L. eruöescens f haingsisiana pictured in pi. III, fig. i — 19 

 and 21 — 22, with the specimens of f. americana reproduced in fig. 15 and pi. III, fig. 20, 

 no difference in habit worth mentioning will urge itself between older and well developed 



1) M. Fosi.ie. New ov critical Lithothamnia. — Det Kgl. Korske Vidensk. Selsk. Skrifter 1S95. Trondhjem 1895, p. 4. 



2) M. Foslie. Calcareous Algae from Fuegia. — Wissensch. Ergebnisse der Schwedischen Expedition nach dtn Magellans- 

 landern 1895 — 97. Stockholm 1900, p. 71. 



SIBOGA-EXPEDITIE LXI. 5 



