28 
WILLIAM KEITH BROOKS 
of blastomeres, the notochord, which later for the most part 
passed into a postero-ventral protuberance there to degenerate 
and share in the formation of the eleoblast which he thus clearly- 
showed to be a degenerate tail ; at one time he was studying struct- 
ures in some of his embryos which seemed to be a pair of true 
stigmata, but his final decision in regard to them is unknown. 
Brooks' embryological work convinced him that Salpa, though 
now perfectly adapted for pelagic Hfe, has not always been pelagic, 
but that it is descended from sessile forms like the ascidians, and 
that some of the features which so well adapt Salpa for a pelagic 
existence arose during this sessile stage in its ancestry, or were 
then much improved over the earlier condition illustrated in 
Appendicularia. Having found this most typically pelagic of 
all pelagic animals to be a migrant from the ocean bottom, he 
was led to review the whole pelagic fauna, and as a result of this 
review reached the conclusion that nearly all pelagic animals of 
considerable size or complex structure have had a similar history 
and are descended from forms that once lived on or near the ocean 
bottom. 
The memoirs upon the Salpidae are of such comprehensive 
character and fundamental importance that they must be desig- 
nated as monumental. This massive character of his work, 
together with the soundness of judgment displayed, has unquest- 
ionably made Brooks the foremost student of the group. It 
is he, more than all others, who succeeded in showing that beneath 
the perplexing maze of secondary phenomena which so obscures 
the development of this group, there is a general conformity to the 
development of other chor dates. 
Researches on the Crustacea.^^ Professor Brooks' interest in 
the Crustacea began early, for as a boy he had collected the fresh- 
water shrimp, Palaemonetes exilipes, in the Rocky River near his 
Cleveland home, and in the marine laboratory of Alexander 
Agassiz he had observed with astonishment "the lively interest 
in shells," displayed by the newly hatched hermit crabs. That 
^'-Professor F. H. Herrick, Western Reserve University. 
