ADVERTISEMENT. V 



His first love for science seems to have grown from liis fondness for flowers. 

 Immediately after leaving college he taught for some time at White Plains, New 

 York. "While there, in some of his out-of-door rambles — and he was fond of takinjr 

 long walks — he found a flower which he thought was new. On returning home 

 he ascertained that it was not described in Professor Gray's Botany. He at once 

 began a correspondence with Professor Gray in regard to it, and eventually received 

 an invitation from him to go to Cambridge. He went there as a student of botany, 

 under Professor Gray, in 1850, and this may be regarded as the date of his scientific 

 birth. While a student at the Botanic Garden, he taught in the Academy at 

 Westfield, Massachusetts, for a single term, apparently achieving much success 

 as a teacher, and forming life-long friendships. 



Soon after this he became a student of Professor Agassiz; but his love for botany 

 never diminished. He studied it in after years from the side of vegetable hitstology 

 and morphology in connection with and as illustrating the histology and moi-ph- 

 ology of animals. The influence of his knowledge of botany on his zoological studies 

 was marked. It prepared him for his studies on spontaneous generation, on the 

 theory of the cell, on the structure of the Protozoa and the nature of protoplasm. 

 In studying tlie lasso-cells of the Acalephs, he traced their analogical resemblance 

 to the stinging hairs of the nettle. By his intimate knowledge of tlie spores of 

 the smaller Algje, he was able to point out some of the characters separating the 

 lowest Protozoa from the spores of plants, and aid in the work of Thuret and 

 others in eliminating from the animal kingdom certain vegetable spores which 

 had been originally described as infusoria. 



His first scientific paper was on a botanical subject, ' The peculiar growth of 

 rings in the trunk of Rhus toxicodendron,^ published in 1856, and this was supple- 

 mented by unpublished studies on the eccentricity of the pith in Ampelopsis quiit- 

 quefolia and Celastrus scandens. In his walks he often botanized, and coutribnted 

 in this way to Gray's botanical text-books. Thus with the training he received 

 from Professors Gray and Agassiz, he looked upon the world of organized beings 

 from both the botanical and zoological sides. He well deserves the name, biologist. 



He graduated from the Lawrence Scientific School in 1854, taking the degree 

 of B. S. He was for several years the private assistant of Professor Agassiz, who, 

 early in 1857, spoke of him enthusiastically, remarking to a friend, 'Clark has 

 become the most accurate observer in the country.' Between 1856 and 1863 he 

 was associated with Agassiz in the preparation of the anatomical and embryological 

 portions of the ' Contributions to the Natural History of the United States.' Here 

 his gi-eat skill and delicacy in the use of the scalpel and pencil won much praise 

 from naturalists. Nearly all the plates in the Contributions, illustrating the 

 embryology and histology of the turtles and Acalephs, are signed with his name. 



