582 Church . — The Structure of the Thaltus of 
N. dumetosa , originally collected by Richard in the Antilles, 
and Harvey in the Friendly Islands, occurs also, according to 
Solms, in the island of Flores and New Guinea. I am in- 
debted to Professor Vines for the opportunity of examining 
spirit-material of this species collected by Mr. H. N. Ridley 
at Singapore. The plants, Mr. Ridley informs me, grow in 
smooth shallow water, attached to mud or piles, and, when 
living, each individual looks ‘ very much like a little green 
sausage.’ They reach a length of 3-5 to 4 cm., and vary from 
2 to 2-5 mm. in diameter ; the main axis is flexible and bears 
a delicately calcified upper portion, ill-adapted to withstand 
damage from rough water or pebbles, thus forming a striking 
contrast to N. Kelleri , Cramer, which is a densely calcified 
and stunted species growing, according to Keller, between 
coral-blocks exposed by the tides. It is possible, therefore, 
that N. dumetosa may prove a more typical species of the 
genus than N. Kelleri. Associated with the adult plants were 
younger specimens in all stages of growth, and in tracing the 
course of development evidence appears to be forthcoming to 
show that N. dumetosa , in consequence possibly of exposure 
to fairly constant and peaceable environment throughout its 
entire life, recapitulates in its ontogeny, not only its own 
phylogeny, but sufficient of that of the whole group of the 
Dasycladaceae to shed light on the relationships of the genera 
comprised in this remarkable order. 
The history of development, in the specimens examined, 
falls naturally into five stages, of which the fifth constitutes 
the adult reproductive form. 
Stage I. 
The youngest plant in the material at my disposal (Fig. 1) 
consisted of an erect Vauckeria-like coenocytic filament, 5 mm. 
in length, attached to the substratum by a typical dichoto- 
mously-lobed basal portion, and bearing at its apex a whorl 
of six dichotomously-branched filaments, delimited from the 
main axis by perforated septa. At points further down the 
axis two other nodes were marked out by the presence of 
