58 THE PEKIODIC GROWTH OF SCALES IN GADID.I; 



apparently be mucli liindered by the latter. The small scales do not 

 appear to be arranged on the skin in the regular manner characteristic 

 of the larger scales, and they do not possess many lines of growth. 

 According to my opinion, these minute scales never grow to any size, 

 and can always be distinguished from the better-developed and more 

 regularly arranged scales. In the early stages I believe that the 

 diminutive scales lie freely and are not covered over by the larger 

 scales ; but as these larger scales grow, they cover over the smaller 

 scales and hinder their growth, consequently the latter either remain 

 small or disappear altogether. That these minute scales grow and later 

 take their place alongside of the larger scales I do not believe. We 

 have also to remember in this connection that the exact number of 

 scales in a row on the fish has been regarded as sutliciently constant for 

 use in the determination of species. 



Klaatsch has referred to these small scales in two connections, firstly, 

 in the development of the trout, and secondly, in a comparison of the 

 teleostean with the placoid scale. He also gives a figure of these small 

 scales in a young trout. In his section dealing with the development 

 of trout scales he says that at the same place in a fish one finds scales 

 which are by no means similarly advanced in development. Between 

 such large scales as already partly cover one another, small scales are 

 very frequently found which are in the earliest stages of development. 

 In older animals such an irregularity does not occur. 



In his section dealing with a comparison of the teleostean and 

 placoid scales, he says that the arrangement of the rhomboid scales on 

 the skin of the trout is similar to the arrangement of the rhombic basal 

 plates of the dogfish ; both of them are arranged in oblique rows. 

 There is a further point of similarity. As in Elasmobranchs, new scales 

 originate in the trout between the well-developed scales ; thus one finds 

 lying between the older scales of the trout even in later stages quite 

 young scale foundations. This irregularity in the early development 

 soon ceases in the trout. 



The Pollack (Gadus pollachius). 



The following tables give detailed measurements of the surface size, 

 number of lines of growth, and annual rings for scales of pollack, which 

 varied from about If inches to 33 inches in length. According to 

 Cunningliam, on the coast of Cornwall the spawning of the pollack 

 commences in February or ]\Iarch, and the young of the year are found 

 in April. In that month they are from y^^ to 1 inch in length, and he 

 estimates their age at approximately six weeks. 



In 1901 I found fish of the latter size, at the beginning of May, 

 possessed of extremely minute scales without any lines of growth. 



