AMPHIDINIUM OPERCULATUM AT PORT ERIN. 393 
to the comings and goings of such microscopic forms and their physiologie al 
inter-relations in connection with what may be called * the metabolism of the 
beach."—W. A. H. 
Sept. Э.е Amphidinium is now baek again in abundance, and the 
Diatoms are absent.—W. А. Н. 
EXPLANATION OF PLATE 18. 
Fig.l. The general appearance of the brown deposits in the ripple-marks on the sand, 
reduced in size, 
2. Naná-grains and Amphidinium (photo-micrograph under low-power magnification). 
3. Sketch from living preparation, to show some Amphidinia resting on the sand-grains 
and others swimming about (low power). 
4. Part of fig. 2 under high-power magnification, 
5. Dorsal and ventral views of Amphidinium operculatum—enlarged from high-power 
magnification. 
For the photo-micrographs reproduced as figures 2 and 4, I am indebted 
to my friend Mr, Edwin Thompson. 
(Reprinted from the Journal of the Linnean Society (Zoology), Vol. xxxii. (1911) pp. 71-5, 
Pl. 8; the original pagination is. given at the bottom of each page. | 
