Lauder^ on New Diatoms, 
7 
(PI. Ill, fig. 1, perfect filament ; fig. 2 a, 4, terminal cells ; 
fig. 3 a, intermediate cell, composed of tlie contiguous halves 
of two separate frustules.) 
For this reason it is that the av/ns at the extremities of the 
filament are always simple, having no other cell contiguous 
to assist in forming the compound bifurcated awn. 
This process of blending and bifurcating in the awns, 
which takes place normally in Bacteriastrum, also very rarely 
happens as an accident or monstrosity in a species of 
Chactoceros (fig. 8) — an exception which serves to strengthen 
the rule with regard to Bacteriastrum. 
From this it will be evident that B. fwcatum, B. curvatum, 
and B. nodulosum, described in Pritchard's ' Infusoria as 
distinct species, are in reality one and the same species, being 
different parts of the filament. 
B. nodulosum is, I imagine, a terminal cell with the 
spirally arranged beads strongly marked. 
The awns of the Hongkong species are always spirally 
beaded, most evident in the terminal cells in the inter- 
mediate cells, the beading on the awns is aborted or very 
indistinct at that part when they blend together, appearing 
distinctly only on their free extremities (figs. 2 b, S b.) 
The diameter of the disc varies from xoVo two •> length 
of the awn is about four or five times the breadth of disc. 
This diatom varies very much in size, and in the number 
and curvature of the awns, but there are no specific dis- 
tinctions sufficiently well marked or constant to warrant its 
division into more than two species. 
Multiplication and reproduction are carried on as in the 
other genera of Chactocerese, by the lengthening of the 
connecting zone of the frustule, the division of the endochrome 
into two masses, and the sprouting of new awns from the 
middle of the frustule ; so that each frustule consists of an old 
and a new valve (fig. 5) . 
At certain times, or under certain circumstances, the 
endochrome does not divide after the lengthening of the 
frustule, but secretes a siliceous envelope, and becomes a 
gonidium or sporangium (fig. 6), consisting of a cell with 
two rounded ends, and a connecting hoop, one end being 
smaller than the other. Prom the smaller end four or 
five slender spines proceed to the sides of the containing 
frustule, and serve as stays or props to keep the gonidial 
body in position ; these bodies always lie with their similar 
ends towards each other throughout the filament. I may 
mention here that these sporangia (if one may call them so) 
of Bacteriastrum and Chactoceros are very variable in form 
