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 G, 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 TV. History of each appendage of Lucifer 92 



SECTION V. The Metamorphosis of Acctes 101 



SECTION VI. Relation between the larvae of Lucifer, Acetes, Sergestes, Peiut-us, and Eaphausia, and 



the significance of the Decapod Zoea, and the Crustacean Nauplius 109 



SECTION VII. Serial homology and bilateral symmetry in the Crustacea 125 



SECTION VIII. 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, GLAUS, 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 



MDCCCLXXXH. I 



