Peculiar Clutch of Blackbird's Eggs. 97 



Thompson (Nature, 4th June 1908, pp. 111-113). The egg, consisting of a 

 slightly extensible membrane filled with an incompressible fluid is subject 

 to external pressure from the radially contractile oviduct, and an equation 

 for the shell can be worked out. It is pointed out that from the nature 

 and direction of the usual peristaltic wave in the oviduct the pressure will 

 be greatest somewhere behind the middle of the egg ; in other words, the 

 tube is converted for the time being into a more conical form, and the 

 simple result follows that the anterior end of the egg becomes the broader 

 and the posterior the narrower. One may recall how the peristaltic move- 

 ments of the intestine in many animals, such as the rabbit, divide the 

 fascal matter into spherical or oval masses. 



The object of the present note is to record a case of variation with 

 subsequent regulation, to show in a collection of hen's eggs how large the 

 crop of variations is, and to note the suggestions that have been offered in 

 interpretations of certain not uncommon freaks, such as a trumpet-shaped 

 egg or an egg within an egg. 



{Issued separately, 11th May 1910. 



