406 POPULAR SCIENCE MONTHLY. 



occupy, they undergo rapid multiplication and growth and build 

 up the tissues of the body, while the scaffolding of follicle cells is 

 torn down and used up as food for the true embryonic cells. An 

 imaginary illustration may help to make the subject clear. Sup- 

 pose that while carpenters are building a house of wood the brick- 

 makers pile clay on the boards as they are carried past, and shape 

 the lumps of clay into bricks as they find them scattered through 

 the building where they have been carried with the boards. Now, 

 as the house of wood approaches completion, imagine the bricklay- 

 ers build a brick house over the wooden framework and not from 

 the bottom upward, but here and there wherever the bricks are to 

 be found, and that as fast as parts of the brick house are finished 

 the wooden one is torn down. To make the analogy complete we 

 must imagine that all the structure which is removed is assimilated 

 by the bricks, and is thus turned into the substance of new bricks to 

 carry on the construction." 



Following that descriptive portion of the work comes a most in- 

 teresting interweaving of facts gathered in wide experience with 

 a scientific imagination possible only to one who had lived and 

 thought in close sympathetic contact with tropical marine life. It 

 is an account of the present conditions of life along tropical shores 

 and the probable steps that led to the evolution of the innumerable 

 sedentary and creeping things from the ancestral forms that floated 

 on the surface of the ocean before there were shores. Charming 

 reading for the layman, and for the specialist a broadening poetic 

 insight into life as it is and as it was when the world was young and 

 the pelagic forbears of the vertebrates competed with their simpler 

 associates in the annexation of the bottom as a vantage ground for 

 the "benevolent assimilation" of later immigrants. The third 

 portion of the work follows a most commendable plan : " Scientific 

 controversy is so unprofitable that I shall try to make it as subor- 

 dinate as possible, that the reader may devote all his attention to 

 the life history of Salpa, without interruption at every point where 

 my own observations confirm or contradict the statements of 

 others." This section deals with the refutation of criticism of the 

 author's interpretations, and endeavors to harmonize the discords 

 that in this, as in all complex morphological research, make prog- 

 ress slow though surer. 



The above brief references to the research work of the subject 

 of this sketch would be too incomplete did we omit mention of his 

 papers upon that very interesting and extremely ancient inhabitant 

 of the Chesapeake, the Lingula, or of the beautifully illustrated 

 memoir of the National Academy of Sciences, describing the crania 

 of the Lucayan Indians, an unfortunate race of gentle beings dis- 



