354: Proceedings of the Royal Physical Society. 



5. Automatic Key. 



Fig. 3, PI. XV., shows a simple key which can be em- 

 ployed as an automatic make or break key. It is fixed to 

 the upper plate of the clockwork (PL XII., Fig. 1) by an 

 adjustable clamp seen in the figure. It is set so that the 

 arm projecting up from the bar of the key is just touched by 

 a light steei spring which can be adjusted to the lower end of 

 the drum, but which is not shown. If the wires are attached 

 at the binding screws on the right, the current will flow 

 through the key when in the position shown. As the point 

 of the drum referred to comes round, it touches the arm, 

 throws over the key, and breaks the current. On the other 

 hand, if the wires are connected to the screws on the left, 

 no current will flow with the key in the position shown, but 

 when turned over by the drum, circuit will be made by the 

 left contact dropping into the mercury cup. 



XXVII. Remarks on the Ovary of Echidna. By Frank E. 

 Beddakd, Esq., M.A, F.R.S.E., F.Z.S., Prosector to 

 the Zoological Society of London. [Plates XVL, 

 XVII.] 



(Read 21st January 1885.) 



During the past year the re-discovery by Mr Caldwell of 

 the long-forgotten fact that the two representatives of the 

 order Monotremata are oviparous, has attracted considerable 

 attention to the group, and, as a result, a number of com- 

 munications on the subject have appeared in various journals, 

 scientific and otherwise. More particularly to be noticed are 

 two reviews — one in Nature} by Mr Baldwin Spencer, and 

 another in Science,^ by Mr J. Gill — which give an account of 

 all the observations concerning the eggs of the Monotremata 

 that had been made previously to Caldwell's telegram to the 

 British Association at Montreal. It appears that Fleming, 

 in his "Philosophy of Zoology" (ii., p. 215), which was 

 published so long ago as 1822, was the first to call attention 



1 December 11, 1884. ^ December 1884. 



