SURFACE DIATOMACEH FROM HONG-KONG HARBOUR. 47 
Mr Thos. Comber and Dr Cleve in place of sporangium, as 
the real function of these bodies is as yet uncertain. 
The endocyst varies in shape according to the species ; 
in some it becomes a body with a capitate head and con- 
stricted neck, the other end being convex, and a broad 
connecting hoop joining them (fig. 5). In others the 
neck is wanting; some have the convex ends smooth, 
others have them studded with spines (figs. 7, 8, and 9); 
others again have the valves produced into two or more stout 
conical horns, simple or branched at the extremities (fig. 6). 
These bodies always lie with their similar ends towards 
each other throughout the filament, and the silica which 
impregnates their cell-walls is much thicker and stronger 
than in the wall of the frustule itself. The endochrome 
is now mostly transformed into a number of spherical, 
highly refractive globules, apparently of an oily nature, the 
filaments become very fragile, breaking up on slight disturb- 
ance, and the enclosed cysts are set free. 
I have been unable to follow out the further processes 
they undergo towards the reproduction of the diatom. 
These curious bodies, which are found in considerable 
number in guano and sedimentary deposits in a detached 
and isolated condition, were, until recent years, usually con- 
sidered to belong to distinct and independent genera, and are 
figured and named as such in works on the subject. For 
instance, several species of Dicladia, Goniothecium, Hercotheca, 
and Omphalothecu are undoubtedly the endocysts of Chetoceros, 
as they have been observed in situ by myself, and more 
recently by Count Castracane, Mr Comber, and others, 
notably from gatherings of oceanic plankton obtained during 
the Challenger expedition. 
These endocysts are not confined to the family under 
consideration, as Mr Comber has, in the Z7vransactions of the 
Royal Microscopical Society, recently described bodies, 
apparently of a similar nature, as occurring in a species of 
Melosira diatom from the Antarctic Sea (Zhalassiosira 
Antarctica). 
The family Chetocerew are divided into the two well- 
marked genera above mentioned :—(1) Chxtoceros (figs. 1, 2, 
and 3), oval in side view, with a single awn springing from 
