336 SUMMARY OF CURRENT RESEARCHES RELATING TO 



certain changes taking place in the ameloblastic secretion, which at first 

 occupies the vacuoles in the ameloblasts, and is then passed through the 

 inner ameloblastic membrane to be deposited on the surface of the 

 dentine. There is probably a gel-formation of the secretion, and then 

 the precipitation of a large amount of the organic material causes a 

 greater concentration of the lime salts in the fluid occupying the inter- 

 spaces, and calcification then progresses until the organic matter is almost, 

 if not quite, calcified. J. A. T. 



Growth of Fish Scales. — A. G. Huntsman {Trans. Roy. Canadian 

 Institute, 1919, 12, 61-101, 17 figs.). The general statement that the 

 growth of the scale corresponds with the growth of the fish, though 

 substantially accurate, requires considerable modification. In fishes 

 belonging to such diverse groups as the Clupeidae {Clupea harengus), the 

 Labridge {Tautoglahrus adspersus), and the Pleuronectidse {Pseudopleuro- 

 nectes americanus) there is a lack of correspondence in the rates of 

 growth of the scales and of the body, as judged by their antero- posterior 

 diameters (particularly as regards the anterior field of the scale). The 

 scale begins its growth later, grows relatively more rapidly than the 

 body during the first half of life, and less rapidly than the body during 

 the second half. 



In the alewife {Pomolohus pseridoharengus) scales from different 

 regions show differences in time of appearance and in rate of growth. 

 The anterior and posterior fields of the scale do not appear at the same 

 time, nor grow at the same rate. The posterior field appears first, grows 

 very rapidly for a short period, and then at approximately the same rate 

 as the entire fish. The anterior field does not grow uniformly, there 

 being a lack of correspondence in the increase not only of the two chief 

 diameters (transverse and longitudinal), but also of the several longi- 

 tudinal diameters (median and lateral). 



There is evidence of a lack of correspondence in growth between the 

 two principal layers of the scale, and even between the parts of one layer. 

 It is suggested that simple variations in the rates of growth of the parts 

 of the scale are responsible for the differences in shape and pattern of 

 scales from different regions. 



As concerns the use of the scales in determining the growth of the 

 fish during the several years of its life, it will depend upon the degree 

 of accuracy desired whether any notice be taken of the discrepancy 

 between the growth of the scale and the growth of the fish. In any 

 case the probable error arising from this source should be considered. 

 It would not be difficult to determine the amount of correction necessary 

 in a particular case. This would be of importance chiefly for the growth 

 during the first year. The best diameter for use in length calculations, 

 if no correction is to be made, is the transverse in the Clupeidae. The 

 posterior field would be preferable, but the indistinctness of the annual 

 rings in that region renders it useless. J. A. T. 



Scale-reading in Salmon. — J. Arthur Hutton (Salmon and Trout 

 Magazine, 1919, August, 1— il). A continuation of careful readings of 

 Bcale-markings and of inferences from data so obtained. By examining 



