20 Museum Notes

PIA talk
B. C. MARINE PLANKTON

Fig. .1. Chaetoceros subtila Cleve. X 600. (Diatom).
“2. ‘Rhizosolenia stolterfolthi Peroj. X 70. (Diatom).

3. Ditylum brightwellt (West) X 70. (Diatom).

4. Noctiluca scintillans (Macartney) X40. (Dinoflagellate).

5. Thalassiostra nardenskioldi Cleve. X 450. (Diatom).

“6. Biddulphia extensa Mann. X 400. -(Diatom).

7. Corethron unguiculatum Comb. forma? X 200. (Diatom).

8. Prorocentrum gracile Brandt. X 800. (Dinoflagellate).

9. Protocystis tridens (Haeckel). X 400. ©(Radiolarian).

“10. Distephanus speculum var regaluris Lemm. X 800. (Silicoflagellate).
“11. The same, separating into two halves and forming a resting spore enclosed
in a colourless, gelatinous, star-shaped investment.

Six representative species of plankton (pelagic) Diatoms are shown in Figs. 1-3, 5-7.
The genus Chaetoceros is represented in our waters by a dozen or more species, some of
which frequently form in the bulk of the phyto-plankton; in the winter they are few or
absent. The species shown in Figs. 2, 3 and 5 are abundant and sometimes dominant ;

Biddulphia and Cerethron occur less frequently, the latter species as found here is
peculiar in having club-like terminations to the short setae.

Noctiluca (Fig. 6) has long been noted for its phosporescent qualities; it is some-
times present in such vast numbers as to colour large areas of the sea.

The small Dinoflagellate shown in Fig. 8 is of common occurrence, and at times is
so numerous as to colour the water.

The representative of the Radiolaria (Fig. 9) occurs at times on the west coast of
Vancouver Island, together with a similar form that has spines around the periphery
(Challengeron armatum f{): only four other species of radiolaria were seen and these
seldom.

The Silicoflagellate shown in Figs. 10 and 11 is common, and occurs in several
varieties; the formation of the resting has not previously been recorded.

Two other species of silico-flagellates are common here—Dictyocha fibula and Ebria
tripartita.

All the above-named organisms are eaten by the pilchard; sometimes half their
feed consists of diatoms.