li CHARLES OTIS WHITMAN 
Whitman was ever keenly alive to the importance of a many sided 
view of animal life and was equally sympathetic to the work of 
the field naturalist and student of ecology and habits, of the sys- 
tematist, morphologist and physiologist in all their multiform 
specialties, requiring only that their work should be thoroughly 
and honestly done. 
His earlier papers especially indicate a real and vital interest 
in systematic zoology and the species question. To whatever 
wide ranging speculations his studies eventually led him, they 
. received their primary impetus through his efforts to find a satis- 
factory basis for the discrimination and definition of the species of 
leeches. Indeed, his very first paper after the publication of 
his Inaugural Dissertation on the ‘‘ Embryology of Clepsine,’”’ was 
on ‘‘A new species of Branchiobdella”’ (B. pentadonta) which he at 
that time, in common with other zoologists, regarded as a leech. 
To such good purpose did he labor that the history of the sys- 
tematic study of the leeches may fairly be divided into a pre- 
Whitmanian and a Whitmanian period. Notwithstanding that 
he often rode rough-shod over many of the most sacred traditions 
of systematic zoology, and notwithstanding that his actual deter- 
minations of species and genera have sometimes proven unfor- 
tunate, nevertheless Professor Whitman discovered the criteria 
by which evolution and specific radiation in the leeches may 
best be measured and expressed, and he set a standard for specific 
description that has since been the guide and model to all the best 
workers in this field. Out of the chaotic condition that Whitman 
found order has been wrought, largely through the use of the tools 
that he devised. It cannot be denied that he imported new light 
and life to the subject, nor that all later students of leeches have 
felt the vivifying influence of his ideals. 
The key to Whitman’s successful analysis of the external mor- 
phology of leeches is his discovery (first announced in two pre- 
liminary papers published in 1884 and subsequently repeatedly 
reverted to and expanded) of the segmental sense organs to which 
he later applied Haeckel’s term ‘sensillae.’ These little, whitish, 
translucent dots, visible on many living leeches, had been noticed 
occasionally by earlier observers and Ebrard had even suggested 
