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II. Lucifer : a Study in Morphology. 
By W. K. Brooks, Associate in Biology and Director of the Chesapeake Zoological 
Laboratory of the Johns Hopkins University, Baltimore, Md., U.S.A. 
Communicated by Professor Huxley, Sec. R.S. 
Received April 6,—Read April 28, 1881. 
[Plates 1-11.] 
Contents, 
Page. 
Section I.—Introductory.... . 58 
Section II.—Segmentation of the egg, and formation of the food-yolk and primitive digestive cavity 64 
Section III.—Metamorphosis of Lucifer ... 72 
Section IY. —History of each appendage of Lucifer ... 92 
Section Y.—The Metamorphosis of Acetes ... 101 
Section VI.—Relation between the larvae of Lucifer, Acetes, Sergestes, Penceus, and Lupliausia, and 
the significance of the Decapod Zoea and the Crustacean Nauplius ... 109 
Section YII.—Serial homology and bilateral symmetry in the Crustacea. 125 
Section YIII.—Explanation of the plates.. 129 
Section I. —Introductory. 
The general anatomy of the adult Lucifer has been satisfactorily made known by 
the observations of Souleyet, Huxley, Hensen, Dana, Semper, Claus, Dohrn, and 
Faxon ; and the only facts which I have to add relate to the structure of the 
reproductive organs. 
The earliest recorded observations upon this subject are by Dana (‘ United States 
Exploring Expedition during the Years 1838, 1839, 1840, 1841, and 1842/ under the 
Command of Charles Wilkes, U.S.N., vol. xiii., part 1). In plate 44, fig. 9, b, h, and 
m', he gives a very correct representation of the male reproductive organs and sperma- 
tophore of an adult male specimen of Lucifer ( acestra ); but his description of these 
figures (p. 670) shows that he was completely at a loss for an interpretation of the 
parts which he has represented, and had no idea of their true function. 
Later students have entirely overlooked these figures by Dana, and there has been 
MDCCCLXXXII. I 
