AS AN INDEX OF AGE, 49 



tion was incorrect (AUgem. Fischerei-Zeit, 1898, Xr. 19), as firstly the number 

 of lamellae is not the same as that of the concentric lines, and secondly the 

 total number of concentric lines is much greater than the number of years. 

 The number of concentric lines which form themselves at the free margin of 

 the lamella stands, however, in direct relationship with the growth of the 

 latter. As a result of this, the comparative distance of the concentric lines 

 from one another also changes ; it is greatest at the time of greatest growth, 

 that is to say, in the summer. 



He gives a diagrammatic transverse section of the scale of a two-year-old 

 carp. He notes the diflficulty of investigations dealing with the compounding 

 of the lamellfe, that is to say, their number in relation to the size of the 

 scale and their relation as a foundation for the concentric lines, as the hardness 

 of their material renders it difficult to secure intact sections. In addition to the 

 concentric lines, there are also radial lines on the surface of scales, the arrange- 

 ment of which he considers to be of some service in the determination of age. 

 He notes the presence of scales which differ in their structure from that 

 described above. This variation from the normal consists of an expansion of 

 the centre of growth so that it sometimes comes to occupy quite an extensive 

 area, and there is a corresponding reduction of the number of concentric 

 lines ; but other scales from the same carp will show usually the normal 

 arrangement. This deformity shows itself in very intensively developed carp, 

 whose quick growth is expressed in the structure of the scale which does 

 not form concentric lines to the usual extent. 



Age-determination from the scale. The hypothesis upon which, in the first 

 place, his method rests is the mode of the carp's life. 



"It is clear, that in an animal which has a so-called winter sleep, whose 

 means of nourishment decreases in autumn at the commencement of colder 

 days, and whose body-weight remains the same in winter-time even under the 

 most favourable circumstances, while in warm months much growth takes 

 place as a result of a rich supply of nourishment, this reaction makes itself 

 evident in a corresponding manner by changes in the structure of the body. 

 We find that this phenomenon is shown, not only in every animal with such 

 a mode of life, but it is true also in the plant world." 



He believes that this change in the nourishment of the fish in summer as 

 contrasted with winter shows itself in the scale as well as in other organs of 

 the body ; but the former is particularly well adapted in its structure to show 

 the effect of the change. 



He says, "As I have now investigated hundreds of carp scales with the 

 most favourable results, I may indeed accept with complete assurance the 

 truth of my hypothesis." 



He acknowledges that one finds individual scales from which age-determina- 

 tion would be difficult, and that there are other scales which would tend to 

 make the inexperienced worker very doubtful ; but the uncertainty disappears 

 after observing several scales from the same fish, as among them some would 

 be found showing more distinct demarcations. 



He then describes the superficial structure of a scale taken from a carp at 

 the end of its second summer, namely, in late autumn, as illustrated by a photo- 

 micrograph. The means of determining the age is, as previously mentiuned, 



NEW .sERIE.s. — VOL. VII. NO. 1. D 



