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1888. | NEW YORK ACADEMY OF SCIENCES. 253 
or lessincorrect. Dr. Holder placed bricks in the water and kept 
them under daily observation, and found that a specimen of 
Meandrina convexa doubled its diameter in one year. This 
test-specimen is in the collection of the American Museum of 
Natural History, New York, and is figured in Holder’s “ Hle- 
ments of Zoology,” page 26, Fig. 24. Experiments with 
branching and other corals showed the rate of growth to be 
much more rapid than had been generally supposed, and many 
valuable notes upon the growth of coral reefs are recorded in 
his works. Dr. Holder made interesting experiments with the 
Physalia, its poison, its parasitic or attendant fishes, the Holo- 
thuria and Fierasper, etc., and sent specimens north of every 
animal found upon the reef. 
He was particularly interested in the flight of birds, and had 
interesting correspondence with Darwin upon the subject. This 
question Dr. Holder reviewed in his last ornithological paper, on 
the flight of birds, read before the New York Academy of 
Sciences, Dec. 19th, 1887. 
When the war broke out, Dr. Holder became acting assistant- 
surgeon in the regular army, and served throughout the war. 
He also was health officer of the post, and had the medical 
charge of the great prison at Dry Tortugas when it was crowded 
with prisoners. Through his personal efforts, funds were 
raised to alleviate the sufferings of the prisoners, who were 
dying of scurvy; and only through his prudence and experience 
was the prison kept from the horrors of epidemics. When he 
was ordered away, and an inexperienced surgeon took his place, 
yellow fever carried off almost the entire post. 
Dr. Holder was a prolific writer, and, while he contributed to 
many scientific publications, he was always impressed with the 
value of creating an interest in nature among the masses. He 
believed that a knowledge of nature and her works would exert 
a refining and cultivating influence; and many of his writings 
tended in this direction. These were on scientific subjects popu- 
larly treated ; his idea being to divest them of technicality, so 
that an interest would be aroused in the study, even among the 
most ignorant. In this,he was eminently successful. He con- 
tributed, in 1867-8, an elaborate series of articles on the Florida 
