CHLOROPHYCEZ 151 
selves gametangia, bearing gametes which conjugate, 
and so form a zygote. 
The Geographical Distribution —The Acetabulariee 
are a tropical and subtropical order. Of the 
fifteen species of Acetabularia, one however occurs in 
the Mediterranean and A. Peniculus on the West 
Australian coast. They occur in all tropical seas. 
Halicoryne has two species, one (H. Wrightiz) in the 
China sea and the other (77. spicata) on the shores of 
New Caledonia. Chalmasia has only one species, 
C. Antillana, and Acicularia is represented alive only 
in the warm Atlantic (West Indies and South 
America). 
Dasycladecce. 
The Thallus—This sub-order is characterised by 
the persistence of the whorls of hairs and by there 
being no distinction between fertile and _ sterile 
whorls—they are all fertile, except locally in the 
joints of Cymopolia—and by the gametangia being 
terminal members of the lateral branches, except in 
Botryophora where they are of lateral origin on these 
branches. 
In Dasycladus the shoot is nowhere incrusted, and 
consists of a short erect axial cell without con- 
strictions or cross-walls, attached to the substratum 
by a holdfast, and clothed with whorls of branches, 
about twelve to each whorl. These are again 
branched in whorls several times, each successive 
whorl diminishing outwards in length and in the 
number of branches. At the apex of the ultimate 
whorl there is produced a single globular sporangium 
