46 



Mr. W. K. Brooks. 



[Apr. 28, 



(3.) The effects mentioned in (1) and (2) are independent of any 

 changes prodnced by the current in the temperature of the wire. 



Finally, certain critical points are alluded to, there being at least 

 two such for each metal, at which sudden changes take place in the 

 ratio of the permanent extension produced by any load and the load 

 itself. 



The existence of the first of these critical points seems to prove 

 beyond a doubt that, in all well-annealed metals, there is a true limit 

 of elasticity, which is intimately connected with the elasticity of the 

 substance, and it will appear from the investigations made in the other 

 parts of this paper, that changes more or less profound take place in 

 most, if not all, of the physical properties of the substance at these 

 points. 



II. " Lucifer : a Study in Morphology.'' By W. K. Brooks, 

 Associate in Biology and Director of the Chesapeake Zoo- 

 logical Laboratory of the Johns Hopkins University, Balti- 

 more, Md., U.S.A. Communicated by Professor Huxley, 

 Sec. R.S. Received April 6, 1881. 



(Abstract.) 



Our knowledge of the life-history of this extremely interesting 

 genus is very scanty, and the only published observations are con- 

 tained in a short paper, without illustrations, in " Proc. Roy. Soc," 

 vol. 24, p. 132, by Willemoes-Suhm. 



The death of this naturalist, only a few months after his paper was 

 written, put an end to his studies, which he had expressed a hope of 

 finishing, and I therefore take pleasure in stating that I have been so 

 fortunate as to procure the eggs of Lucifer, and to trace every stage of 

 the metamorphosis, from the time the larva leaves the egg up to the 

 mature male, by the actual moulting of isolated specimens in captivity ; 

 and I have also been able to add a few observations upon its em- 

 bryology. 



The early stages of development are extremely interesting, since the 

 segmentation is quite different from that of any arthropod egg which 

 has been described. The egg undergoes total regular segmentation ; 

 there is a true central segmentation cavity, and during the early 

 stages there is nothing to represent the yolk-pyramids of the ordinary 

 crustacean egg. When segmentation is somewhat advanced, the 

 granular matter becomes restricted to one of the spherules ; this then 

 pushes into the segmentation cavity, and appears to correspond to 

 a single yolk-pyramid. Its outer end splits off as a blastoderm cell, 



