190 THE AMERICAN NATURALIST. [Vor. XXXVI. 
avidity. There were more copepods in the red streaks than 
in the intervening bluer water. I was not able to see any 
Gonyaulax in them, however. 
Gonyaulax undoubtedly produced its harmful effects by dying 
in enormous numbers, the putrefactive changes thus occasioned 
polluting the water and giving rise to the stench already men- 
tioned. It died most rapidly along the water's edge, thus affecting 
the littoral animals especially. 
When placed under the microscope for examination in a drop 
of water, many Gonyaulax soon became quiescent, and the pro- 
toplasm drew away from the cuirass, forming a spherical cyst, 
which was often discharged by a rupture of the cuirass along 
any sutural line. - Others died outright and disintegrated, leav- 
ing only the transparent, colorless cuirass. This tendency to 
die readily was noted long ago by Darwin for a species of 
dinoflagellate found in swarms off me western coast of South 
America. 
With this pines abundant species other species of Dino- 
flagellata were found: Ceratium furca, C. fusus, C. michaelis, 
Peridinium divergens, Prorocentrum micans, Polykrikos sf., 
Dinophysis Sp-s Noctiluca sg., and certain swarmspores resem- 
bling those of Peridinium ovatum. The most abundant of these 
was Noctiluca, toward the end of July, but it did not begin to 
approach Gonyaulax in numbers. Where there was one Noc- 
tiluca there were hundreds, if not thousands, of the other form. 
The latter was present in the tow as early as June 17, in 
company with, and about as abundant as, the above-named spe- 
cies. All of these species increased during July, but Gonyaulax 
outstripped the others remarkably. The cause of this increase 
of one species over these closely related ahd associated species 
is not clear. I did mot see a single case.of fission, but the 
individuals varied so greatly in size as to suggest rapid repro- 
duction, probably by encystment and spore formation, though 
no spores excepting the large Peridinium (?) swarmspores were 
seen. Noctiltica was sporulating at this time. It. is possible 
that the immense patches of Gonyaulax . were brought in by 
currents from: ner water. Nothing, however, -was seen of 
them throughout the season around Santa Catalina Island, 

