124 BRITISH BIRDS. [vol. x. 



tl e method of teaching the young the first elements of procuring their 

 own food. This year, about a week ago, I watched the same 

 performance, Helen M Rait Kerr. 



Rathmoyle, 

 King's Co., 



August 7th, 1916. 



DIRECTION OF MARKINGS ON TERNS' EGGS. 

 To the Editors of British Birds. 



Sirs,— I was interested in reading Mr. W. Rowan's note {supra 

 p. 96) on the twisted markmgs seen on some Terns' eggs. I found 

 that those in my collection both Common Tern (Sterna hirundo) and 

 Sandwich Tern (Sterna s. sandvicensis) had the twist shewing from 

 right to left, and not as shewn in Seebohm's plates from left to right. 

 Dresser, however in his Eggs of the Birds of Europe, has the twist fairly 

 clearly shewn in one or two cases, always from right to left. The 

 plates in this work were photographed direct from the specimens by a 

 three-colour process which would shew the eggs in the correct 

 position. The same thing may be noted in Kearton's British Birds' 

 Nests, where the coloured figures are well reproduced by a similar 

 process direct from the eggs. 



The question, however, is, do all eggs rotate from left to right in their 

 passage down the oviduct and if so how are the very distinct blotches 

 and spots formed. In this connection I would draw the attention of 

 those interested in the subject to a very comprehensive and well 

 illustrated article by Dr. R. W. Shufeldt in The Emu for April 1916, 

 Vol. XV., pp. 225-34. The title " Eggs of Reptiles and Birds compared " 

 is rather misleading, as the article deals nearly altogether with the 

 coloration of birds' eggs and speculation as to how the colour is 

 applied. The following extract taken from the last paragraph, 

 pp. 231 and 232, gives Dr. Shufeldt's summing up and I think throws 

 some light on the beautiful marking of Terns' eggs. 



" Now, in these eggs of the Australian Magpie we have both hair-line 

 markings and spots on the same specimens ; some of these may be 

 sharp and others blurred, while there may likewise be massing of the 

 different markings at the butt on the same egg. These may all be 

 explained through what I have attempted to set forth in previous 

 paragraphs of this article, as any egg passing down the oviduct (either 

 butt or apex first ) may f ometimes be at rest ; sometimes — either slowly or 

 rapidly — advance without rotation, or various rotary movements may 

 be imparted to it through the peristaltic and anti-peristaltic contrac- 

 tions of the walls of the oviduct — the pigmentary glands being function- 

 ally active all the time in those cases where pigment is being 

 deposited." 



LiSMORE, Belfast. W. H. Workman 



September 8th, 1916. 



