MancJiester Memoirs, [W. /zvV. (1913), A'^. 3. / 



' ridges,' but which I shall term annuli (see photo of 

 scale A). These annuli are arranged in a roughly con- 

 centric manner from the centrum of the scale iC). . . . 

 Examination with the low power of the microscope shows 

 that the annuli are arranged in a definite manner, some 

 far apart and others close together. Those far apart are, 

 according to Mr. Johnston, formed during the rapid 

 growth of the fish in the summer, and those closer 

 together during a time of slow increase in the winter. 

 This formation of annuli far apart, together with the for- 

 mation outside this of annuli more closely placed, was 

 called by Mr. Johnston an ' Annual ring.' For this name 

 the word ' Peronidium ' is substituted, and it is used to 

 indicate the growth which takes place in a complete 

 summer and winter." 



Unfortunately I overlooked a paper by Professor 

 T. D. A. Cockerell, published early in 191 1 (7), in which 

 he also gives terms for the different parts of the scales. 



"The key to the origin of the sculpture of a teleos- 

 tean scale is apparently to be found in that ancient type 

 Mh^ Amia m/z'^? of North America. Pig. i .shows part of 

 the base of the scale of this fish, which, it will be observed, 

 consists of longitudinal strands or fibres, separable ele- 

 ments which fray out basally. In the apical field these 

 are directed towards a rough nucleus area. A close 

 approximation to this is found in a very old type of 

 teleosteans, the lady-fish Albula. In this, however, appear 

 also the beginnings of the radial lines, extending from the 

 nucleus of the scale to the margin. As we go higher in 

 the scale of fish evolution, these radiating lines or radii 

 often become very prominent, while the longitudinal 

 strands usually become united above and below, forming 

 circular fibres which we have designated circuli. The 

 nomenclature of these structures was based on a normal 

 highly-develo[)ed scale, in which the circuli deserved their 



