284 



Mr. J. F. Bullar on 



[Apr. 4, 



but these lines, which are reversed, are of such great width that it is 

 at present impossible to say whether they are coincident with lines in 

 the solar spectrum. 



April 4, 1878. 



Sir JOSEPH HOOKER, K.O.S.I., President, in the Chair. 



The Presents received were laid on the table, and thanks ordered 

 for them. 



Notice was given that, with a view to facilitate observation of the 

 Solar Eclipse of July 29, the Pennsylvania Railroad Company will 

 convey observers, being private persons, from Philadelphia or New 

 York to Denver and back at reduced fares. 



The following Papers were read : — 



I. " On the Development of the Parasitic Isopoda." By J. F. 

 Bullar, B.A., Trinity College, Cambridge. Communicated 

 by Dr. Michael Foster, F.R.S., Prelector of Physiology in 

 Trinity College, Cambridge. Received March 14, 1878. 



(Abstract.) 



The paper contains an account of some points in the development 

 of the Gymothoa oestroides and G. parallela of Milne-Edwards. 



The work was mainly carried on in the Zoological Station at Naples, 

 and the author takes this opportunity of returning his best thanks to 

 Dr. Dohrn and Dr. Eisig for the kind way in which they forwarded 

 his researches. 



The eggs were prepared in the way described by Bobretzky in his 

 paper on the development of Oniscus murarius ("Zeit. fur Wiss. Zool." 

 Bd. xxiv), namely, by heating them in water, and then hardening 

 them, first in bichromate of potash, and then in alcohol, beginning with 

 70 cent, and gradually increasing the strength to absolute. The sec- 

 tions were stained with Kleinenberg's hematoxylin and mounted in 

 Canada balsam. 



The eggs when first laid are surrounded by a single membrane. 



The earliest stages of segmentation were not observed; the first 

 described is that in which a circular patch of cells has appeared at 

 one pole of the egg. The cells are of considerable size and contain 

 very large granular nnclei ; in the centre of the patch they are poly- 

 gonal, and more than one layer deep, but at the edges they are flat- 

 tened and form a. single layer. 



The blastoderm gradually spreads over the yolk, the cells on the 



