340 Development of Apteryx. Electrical Resistances. [Jan. 21, 



III. " Additional Observations on the Development of Apteryx" 

 By T. JEFFEEY PARKER, B.Sc., F.R.S., Professor of Biology 

 in the University of Otago, Dunedin, New Zealand. Re- 

 ceived December 15, 1891. 



(Abstract.) 



The paper is founded upon the study of three embryos of Apteryx 

 australis obtained since the author's former communication on this 

 subject was written. 



The youngest (stage E') is intermediate between E and F of the 

 former paper, the next (F') between F and G, the most advanced 

 (G') between G and H. 



In E' the characteristic form of the beak has already appeared. 



In F' the pollex is unusually large, giving the fore-limb the normal 

 characteristics of an embryo wing. 



Several important additions and corrections are made to the former 

 account of the skull, especially with regard to the pre-sphenoid 

 region, the basi-cranial fontanelles, and the relations between the 

 trabecular and para-chordal regions. 



The account of the shoulder-girdle is amended. In Apteryx oweni 

 the coracoid region is solid, and no pro-coracoid appears ever to be 

 formed : in A. australis a ligamentous pro-coracoid is present at a 

 comparatively early period (stage F' and perhaps E'). 



An intermedium is present in the carpus in all three specimens in 

 addition to the elements previously described. 



The brain in stage G' is interesting, as being at what may be called 

 the critical stage ; the cerebellum is fully developed, and the optic 

 lobes have attained the maximum proportional size and are lateral 

 in position. In all essential respects the brain of this embryo is 

 typically avian. 



IV. " On a Differential Electrostatic Method of measuring High 

 Electrical .Resistances." By Major CARDEW, RE. Com- 

 municated by Sir WILLIAM THOMSON, D.C.L., P.R.S. 

 Received January 6, 1892. 



The following method has been found useful for determining the 

 relative value in insulating quality of small samples of materials, the 

 insulation resistance of short pieces of cable, and other very high 

 resistances. 



The arrangement is also suitable for continuously indicating the 

 position on any electrical circuit, worked at a high pressure, of the 



