140 



CEYLON MARINE BIOLOGICAL REPORTS. 



In the island of Jaffna in the north of Ceylon I found some peculiar specimens of a very exceptional 

 appearance. It is these that I have described as /. mixta (figs. 49, 50). In all respects it is more slender 

 and weaker than the preceding form. In addition to small pedunculated vesicles with constrictions below 

 the top, it has pear-shaped branchlets, clearly indicating opposite arrangement just as in /. geminata, 

 Harv.; finally, and this is the most characteristic feature, some few branchlets grow out cylindiically to a 

 breadth of 3 mm. , and show themselves to be of the same shape as C. ambigua Okamura (c/. Okamura , 

 •'Algae from Ogasawara-jima." PI. 1, figs. 4, 6, 7). 



Oeographical distribution. — Ceylon : Dondra Head ! Matara ! Weligama (/. crassicaulis) ! 

 in the last named place at a depth of about 1^ to 2 metres (at low- water) inside the reef together with 

 C. sertularioides and C. taxifolia ; in the other, places in tlie upper littoral zone ; Jaffna (/. mixta) ! Indian 

 Ocean ; Pacific Ocean. 



C. sedoides in a wide sense is known from Australia, New Zealand, and Tasmania in the south. 

 From Ceylon, the Gulf of Siam (Schmidt) in the north, and to the Friendly Islands in the east. 

 Tiie different forms seem to have their different limited districts: thus,/, tasmanica and geminata have 

 exclusively southern distribution (Australia and Tasmania), whereas /. crassicaulis has exclusively 

 northein, true tropic distribution (the tropical coast of Australia, Ceylon to Friendly Is.). This possiblj' 

 points to the fact that these forms liave rather the character of different races or elementary species, 

 an inference that is furthermore strengthened by the fact that, as I have mentioned above, /. crassicaulis 

 in Ceylon is constant and uniform. Against this, /. wixto seems more local, and, as I have above tried to 

 show, its peculiar branching may probably be explained as a kind of atavistic bud- variation. > 



21.— CAULERPA FERGUSONIi (Mibray). 



Murray. On some new species of Caulerpa, p. 212, pi. 53, fig. 1. 



Weber v. Bosse, Monograpliie des Caulerpes, p. 389 (sub nom. C. Fergusoni). 



Exsicc. : Ferguson, Ceylon ^Vlgse, No. 415. 

 This Caulerpa, only known from Ceylon, I have observed once at Paumben Pass, and there very 

 scantily, growing on mud or slime together with C. longistipitata and Enalus acoroides. To the description 

 of this plant, which we owe to Murray, the following may be added : — 



coarse 



Fig. 51. — C. Feif/utionii. mubb. (1 X 1). 



It does not seem to be uncommon for the branched stem, when situated horizontally, to form 

 i roots downwards and jointed side branches upwards. Fig. 51 a and fig. 51 b show this case, 



