No. 3.] AMERICAN ASSOCIATION. 161 



the fused mass. The presence of metiUic iron at the same time 

 he explained as the result of a partial dissociation of the double 

 sulphuret on cooling. His inquiries in this matter are not yet 

 finished, but throw an unexpected light on some furnaee reactions, 

 as the treatmeiit of iron in the Bessemer process, and also on the 

 production in nature of many igneous rocks. 



-EMBRYOLOGY OF LIMULUS, WITH NOTES ON THE AFFINITIES. 



By A. S. Packard, M.D. 



In a reeeEt paper on the embryology of Limulus, published ia 

 the memoirs of the Boston Society of Natural History, I stated 

 that the blastodermic skin just before being moulted consisted of 

 nucleated cells ^ and also traced its homology into the so-called 

 amnion of insects, I have this summer, by making transverse 

 sections of the egg, been able to observe in a still more satisfac- 

 tory manner theee blastodermic cells and observe their nuclei 

 4>efore they become effaced during or after the blastodermic 

 .moult. 



On June 17 (the egge having been laid May 27) the periphe- 

 ral blastodermic cells began to harden, and the outer layer — that 

 destined to form the amnion — to peel off from the primitive band 

 ^beneath. The moult is accomplished by the flattened cells of 

 the blastodermic skin hardening and peeling off from those be- 

 ;iieath ; during this process the cells in this outer layer losing 

 their nuclei, and, as it were, drying up, contracting and harden- 

 ing during the process. This blastodermic moult is comparable 

 with that of Apus, as I have already observed, the cells of the 

 J)lastodermic skin in that animal being nucleated. 



The paper eet f»rth that while the process above described 

 resembled features in the development of the scorpion, and thus 

 strengthened the supposition of Burmeister, that the Limulus is 

 related to the epdders, nevertheless other features which Prof. 

 Packard pointed out led him to believe that the Limulus is re- 

 lated to the lower crustaceans, but is, like all the earlier or palae- 

 ozoic types, oGmprehensive or synthetic, comprising certain fea- 

 tures belonging .to higher forms, while yet holding its proper 

 nffinities with the lower ones. He also confirmed the brilliant 

 xesearches of A. Milne Edwards upon this representative of aa 

 .raacient type. 



