730 
each one irrespective of the other, from the 
continuous, onward stream of cytoblastema.” 
He says, further, that “all Rhizopods are 
moving, sentient masses of Cytoblastema, and 
that alone.” 
Clark was admirably adapted by nature for 
doing histological work of the highest order. 
He possessed that philosophic insight of the 
true naturalist which often enables him to 
divine much further than he can perceive in 
the tracing of relationships and to anticipate 
what the microscope is to reveal. At the time 
he began his work as an observer, zoological 
science in America was especially deficient in 
histological investigations, and he did more 
than any one else to remove this reproach 
upon American biology. 
“Henry James Clark,” said Asa Gray at 
the time of his death, “ deserves to be enrolled 
in the list of botanists. Although his high 
reputation was won in another department, he 
was an excellent botanist before he became 
Mr. Agassiz’s assistant and gave himself to 
zoological investigation: the present writer 
was indebted to him for more than one inter- 
esting discovery of points of structure. He 
is thought to have been the ablest microscopic 
investigator which this country has produced.” 
“His labors as a zoologist,’ said James D. 
Dana, “especially in those departments re- 
quiring difficult microscopic research, had 
placed him among the two or three first in the 
country, and given him a world-wide reputa- 
tion. He was always working, and full of 
enthusiasm in science, and also a most genial 
and excellent man.” 
In the preface to volume one of the “ Con- 
tributions to the Natural History of the 
United States,” dated October 8, 1857, Pro- 
fessor Agassiz says: 
Mr. H. James Clark has assisted me from the 
beginning of my investigation of the embryology 
of these animals, and drawn, with untiring pa- 
tienee and unsurpassed accuracy, most of the 
microscopic illustrations which adorn my work. 
I owe it to Mr. Clark to say, that he has identified 
himself so thoroughly with my studies since he 
took his degree in the Lawrence Scientific School, 
that it would be difficult for me to say when I 
SCIENCE 
[N.S. Vou. XXXV. No. 906 
ceased to guide him in his work. But this I know 
very well, that he is now a most trustworthy ob- 
server, fully capable of tracing for himself the 
minutest microscopic investigation, and the accu- 
racy of his illustrations challenges comparison. 
In a lecture given at the summer school 
of Natural History at the Island of Penikese, 
early in July, 1873, Professor Agassiz an- 
nounced the death of Professor Clark and 
spoke in the highest terms of his work and of 
him as a man. He said that as a micro- 
scopist and histologist he regarded him as 
fully equal if not superior to Ehrenberg, who 
was at that time considered the best in the 
world. 
Professor Fernald, to whom we owe the de- 
partment of entomology in this college and 
in whose honor we are gathered to-day, has 
expressed the opinion that he was the most 
brilliant of all the young men that Agassiz 
drew round him when he first came to this 
country; that as an artist in illustrating his 
work he probably had few if any equals, and 
as an observer and investigator he must be 
placed in the front rank of the naturalists of 
his time. In marine zoology he probably had 
no superior, and if his life had been spared he 
would undoubtedly have left a marked impress 
on the college. 
Three things can be said of Clark. He was 
a genius, he had the best of teachers, and he 
made the most of his opportunities. The se- 
cret of his success as an investigator may be 
stated in his own words taken from his diary, 
where he says, “I made it a rule to practise 
the utmost rigidity and thoroughness in my 
researches, without regard to time consumed 
or the value of the results.”” Such was the 
life of Henry James Clark, full of supreme 
devotion to science and showing an indom- 
itable energy in the search for truth.” 
FREDERICK TUCKERMAN 
? Several species bear his name. Agassiz dedi- 
cated to him the acaleph, Idyiopsis clarkii; 
Biitschli the animaleule, Salpingeca clarkii—a 
name later bestowed by Stein upon another form 
of the same genus. His services are also com- 
memorated in Ascortis clarkti of Verrill, the most 
delicate species of calcareous sponge found on our 
coast. 
