WILLIAM KEITH BROOKS — CONKIJN 



tacea,* and altogether about fifteen papers dealing with these 

 subjects were published during a period of fifteen years, from 

 1879 to 1892, his first contribution on the larval stages of 

 Squilla empusa representing some of the "Scientific Results of 

 the Chesapeake Zoological Laboratory" for 1878. At Beau- 

 fort, in 1880, his interest in this subject deepened, for he saw 

 in the structure and metamorphosis of these animals a means 

 of attacking several larger problems, such as the laws of larval 

 development, the analysis of secondary adaptations, and the 

 meaning of metamerism in both lower and higher animals. 



The works by which Professor Brooks will be best known to 

 all future students of crustacean zoology are undoubtedly his 

 large monograph on "Lucifer: a study in morphology," pub- 

 lished in the Philosophical Transactions of the Royal Society 

 of London for 1882, and his "Report on the Stomatopoda," 

 which appeared as part of the sixteenth volume of the Sci- 

 entific Results of the Challenger Expedition in 1886. Not 

 only did he discover that the shrimp, Lucifer, emerged from 

 the Qgg as a true Nauplius, but, what was even more novel, 

 that the Qgg itself underwent a total and regular segmentation, 

 and gave rise to a gastrula of the invaginate type. After 

 tracing the metamorphosis through nine distinct stages, and 

 making exhaustive comparisons, he concludes that the highly 

 peculiar segmentation and gastrulation are secondary, but that 

 the three-jointed Nauplius represents a true ancestral form, 

 "and nothing but the supposed necessity of believing that the 

 primitive Crustacea had a large number of somites and ap- 

 pendages opposes this view." He shows that the serial and 

 bilateral homology, so evident in the Crustacea, cannot be ex- 

 plained by supposing that the ancestors of the Crustacea repre- 

 sented a community of independent parts. In his Report on 

 the Stomatopoda he considers this subject again, and concludes 

 that serial homology may be due "to heredity from the same 

 part of the developing tgg, rather than from a remote an- 

 cestor." The report on the Stomatopoda is distinguished by 

 the great ingenuity and mastery shown in classifying all of the 



*For assistance in preparing" this abstract of Brooks' work on the 

 Crustacea, the writer is indebted to Prof. F. H. Herrick. 



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