1896-97.] Mr George Murray on Marine Diatoms. 
207 
On the Reproduction of some Marine Diatoms. By 
George Murray, F.R.S.E., F.L.S., Keeper of Botany, 
British Museum. (With Three Plates.) 
(Read December 7, 1896.) 
The subject of the production within Diatoms of spores, en do- 
cysts, &c., has been worked at by several observers, principally 
Castracane * in recent years, and before him O’Meara f and Raben- 
horst.J Some of these observers have noted ciliated, sporedike 
bodies, probably parasitic or casual intrusive organisms ; others, 
notably Castracane, have recorded oval and other cysts which have 
not been figured and the characters of which are difficult to realise. 
Miquel§ has made an experimental examination of the subject 
without being able to confirm Castracane’s results. Castracane || 
has also recorded the presence, as he thinks, of “gonids or embryo- 
nal forms ” within a fossil Diatom ( Coscinodiscus punctatus ) in 
a marine deposit of miocene age. During March of this year I 
tow-netted near the Bell Rock a large quantity of Coscinodiseus 
concinnus — with many dead valves separated at the girdle. 
These frequently contained not only other and smaller individuals 
of the same species, but other species of diatoms and casual objects 
as well, and the observation makes one cautious about accepting 
evidence of the character brought forward by Castracane as to his 
fossil form. 
Lauder, H in describing forms of Bacteriastrum and Choetoceros, 
observed the formation of endocysts. “ At certain times, or under 
certain circumstances, the endochrome does not divide after the 
* Le Diatomiste, ii. (1893) ; Atti Accad. Pontif. Nuovi Lincei , xlvii. (1894), 
French ed. in Le Diatomiste, ii. (1894) ; Atti Accad. Pontif. Nuovi Lincei, 
xlviii. (1895). 
t Anthozoids in Plcurosigma Spencer if Proc. Dull. Soc. Nat. Hist. (1856) 
and Quart. Journ. Micr. Sci. (1858). 
X Conf. Carpenter on the Microscope, ed. vii., by Dallinger, 1891, p. 526. 
§ Le Diatomiste, ii. (1893). 
|| Atti Accad. Pontif. Nuovi Lincei (1885). 
IT Trans. Micr. Soc., vol. xii., n. s., 1864, pp. 7 and 75. 
