large and strongly faceted. The mouth parts are entirely absent, their 

 place being taken by supplementary eye spots. The function of the 

 male insect is simply to fertilize the female, and it then dies. The 

 number of generations annually among bark lice differs so widely with 

 different forms that no gei 



EMBRYOLOGY. 1 



The development of Isopods.— Last Winter when M. Louis 

 Roule published a long paper in French on the development of an Iso- 

 pod, Porcellio scaber Leach, it seemed advisable to present a rather full 

 abstract in this magazine, for the benefit of those readers who would 

 not see the original or who did not read French. That abstract ap- 

 peared in February and contained, besides the descriptive account of 

 the embryology, some interesting conclusions based on these results. 



In the May number of the Journal of Morphology Dr. J. Playfair 

 b publishes a long paper, illustrated with excellent figures, 

 which is not at all reconcilable with M. Roule's views. It must be re- 

 membered, in comparing the two papers, that M. Roule studied a single 

 species of Isopod, that he gives rather diagrammatic figures, and that 

 his description of the segmentation, on which apparently the whole 

 fabric rests, is of a very general nature. 



Dr. McMurrich took up the work in 1890, hoping to make out the 

 cytogeny of a Crustacean as Whitman had done for Clepsine, and 

 as E. B. Wilson has later done for Nereis and other forms. This 

 author's results rest then on a thorough study of the segmentation, and 

 as he did not confine his attention to one form, but observed and figured 

 the segmentation and early differentation in a number of Isopods, the 



The forms studied were Jcera marina Mobius (1873); Asellus communis 

 Say; Porcellio scaber ; Armadillidium vulgare ; with some observations 

 on Cymothoa and Ligia. 



The segmentation is centrolecithal. The nucleus of the unsegmented 

 ovum lies in a central mass of protoplasm surrounded by yolk, and 



1 Edited by E. A. Andrews, Baltimore, Md., to whom abstracts, reviews and 



