ox THE DEVELOPMENT OP LIMULUS LONGISPINA. 57 



before heating by applying the points of two fine needles from opposite 

 points at the same time. 



For the surface- view of the embryo, the ventral plate was peeled 

 OÏÏ from the underlying yolk of the preserved egg, and was stained 

 with borax carmine, then washed in acidulated alcohol, and after de- 

 hydration and clarification was imbedded in Canada-balsam. 



For the sections the eggs were stained with borax carmine or 

 haematoxylin in tofo. As the yolk is very abundant, the sectioning 

 was very troublesome. In the case of the early stages in which the 

 dorsal part consists only of the one- cell layered epiblast, I cut away 

 this part as much as possible. By using the celloidin-parafiin 

 method of imbedding I obtained very good sections. 



I am sorry that I couJd not observe thoroughly the whole 

 developmental history of the Aty 6 »%(YW?', for want of sections of eo-os 



Co 



of very early and of very late stages. My observations were made 

 chictly on the stages from the formation of the germinal layers to 

 about two weeks before hatchino-. 



External Changes. 



On July 29th, 1890, 1 dug out two series of the spawn, whidi 

 liad been laid on the morning ol the same day, traiisfcrred them into 

 the box before mentioned, and examined and preserved eo-os froni 

 them every day. 



On August 2nd (5 days after spawning), I saw many irregular 

 furrows on oriC pole of the egg (fig. 2). This was the first surface 

 change I observed. These furrows were observed by Osborn'^ in the 

 American Li und us. 



\) Oshovu—}rrlumorphusi.< of I.imiilti.^ poli/phnnu.^. Johns llopkin's Tniv. Circ. vol. 'S'. 18Sr>. 



