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 life, 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 Salpidse 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 chordates. 



Researches on the Crustacea. 13 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 



11 Professor F. H. Herrick, Western Reserve University. 



