RHYTHMIC NATURE OF ANIMALS AND PLANTS—BROWN 387 
ones. Like the boxer in the ring, the organism in its rhythmic en- 
vironment is able to yield before the periodic blows and to advance 
after them. In its rhythmic physical environment, the rhythmic 
organism is therefore adapted, figuratively speaking, to make hay 
while the sun shines, in preparation for the dark, cold nights. 
The spectacular, complex character of the rhythmic nature of living 
things first impressed me about 25 years ago as a young visiting in- 
vestigator at the Bermuda Biological Station. One of the fascinating 
pastimes was to sit on the laboratory jetty in the evening after dark 
with the water beneath illuminated by an electric lamp. Myriads of 
living things, attracted by the light, would swim into the area. All 
the creatures were easily identified because biologists had thoroughly 
studied the flora and fauna of the Island and published extensively 
upon them. But one night about 10 o’clock, the water suddenly be- 
came charged with ghostly, transparent, strange shrimp. We cap- 
tured some but a careful search revealed that these had never before 
been seen at Bermuda. They were sent to the British Museum, where 
it was learned that only one male specimen had ever before been 
caught—and that one in the Indian Ocean about 50 years earlier. 
It turned out that these shrimp are abundant at Bermuda, but swarm 
in hordes only for an hour or two just before midnight near the time 
of new moon. A 2-year study by Wheeler of the fluctuation in 
abundance of these shrimp at different times of the lunar month 
showed one swarming peak to occur two days after new moon, and 
a second larger one 3 to 4 days before new moon. No one knows yet 
where they conceal themselves the rest of the time. 
Such a precise lunar rhythm of swarming to assure the bringing 
together of large numbers of males and females for breeding and 
maintenance of the species is commonplace. Another and better- 
known example of lunar swarming for breeding purposes is that of the 
palolo worm of the southwest Pacific. At a predictable time of day 
at the times of the October and November third quarter of the moon, 
elongated posterior ends of these worms, filled with reproductive cells, 
break off and swarm from the burrows in the coral rock in such num- 
bers that they are readily scooped out of the sea. The predictable 
occurrence of these delectable, edible worms determines the time of 
feast days for certain South Sea islanders. 
Coming closer to home, newspapers of coastal areas of California 
indicate for their readers the exact hour when they can go to their 
sandy beaches and expect to catch a highly prized, small edible fish, 
the grunion, as they swarm in from the open sea and throw them- 
selves onto the beaches. This they do from April through June at 
that exact time of the month when the sun and moon are cooperating 
to produce the highest high tide of the month, and a few minutes after 
