TRANSACTIONS OF SECTION D. 661 



for the most part implanted in sockets on the upper surface of the fibrous 

 stratum with a varying inclination. Those at the centrum appear to have fused, 

 forming a horizontal plate, while at the periphery of the scale they are almost 

 perpendicular. In a section through the skin of a green cod about 4 cm. long, 

 the individual scalelets are quite isolated. Each consists of a basal plate, from 

 the upper surface of which projects a minute spine, thus resembling a small 

 placoid scale. Such a condition "is only evident in material from which acid has 

 been rigidly excluded. This condition does not appear to have been previously 

 noted ; the figures given by Klaatsch and others being similar to those which I 

 obtained from material which had been passed through acid alcohol, and which 

 do not show the true nature of the scale. 



WjEDJVESDAY, SEPTEMBER 17. 



Discussion ttpon Mimicry and Natural Selection. 

 Oldened by Professor E. B. Poulton, F.E.S. 



The following Paper was read : — 



Some Remarks on Early Development of the Head kidney in Polygordius 

 and Eiqoomatus. By C, Shearer. 



