660 REPORT— 1902. 



Decrease of Species. 



The Crane abounded in the twelfth century, the Capercaillie until the eighteenth 

 century, the Bittern bred in the nineteenth century, tbe Common Buzzard until 

 about 1883, the Red-throated Diver until about 1896, -while the Woodlark, 

 Raven, Marsh and Hen Harriers, Golden and White-tailed Eagles, Quail, and 

 Roseate Tern are approaching extinction. 



The Great Auk appears to have been at one time not uncommon on several 

 parts of the Irish coast, for Mr. Knowles has discovered its remains in Co, Antrim. 

 I have found the bones of six or eight individuals on the Waterford coast, and 

 other bones have been obtained in 1902 in Co. Clare. In each case the remains 

 of Great Auk were found in kitchen middens, with other bones used for food by 

 the ancient inhabitants, by whom this bird was evidently captured. 



1 0. On the Structure of the Scales in the Cod. 

 By H. W. Marett Tims, B.A., M.D. 



The development of scales in various fishes has been described by several 

 writers, notably by Hertwig and Klaatsch, the latter dealing also with many of 

 the morphological aspects. There is, however, an almost entire absence of 

 detailed observations as to the structure and pattern of the fully formed scales, 

 and some of the transitional stages in the growth of the scale appear to have 

 escaped observation. 



Through the kindness of Professor Macintosh, F.R.S., I have been enabled to 

 work at this subject during tbe past few weeks in tlie Gatti Marine Laboratory at 

 St. Andrews. 1 have confined my observations in the first instance to the scales 

 of the Gadid.'B, the species examined being G. virens, G. morrhufP, G. pollarchn.s, 

 and G. leitcus. The younger stages were taken from Professor Macintosh's rich 

 stores, while the older were mostly from material freshly caught. 



The formed scale is a compound structure consisting of a fibrous stratum upon 

 the upper surface of which are situated numerous ' scalelets ' arranged in lines 

 radiating from a more or less homogeneous centrum. The form of these scalelets 

 varies somewhat in the diff"erent species, and to a certain extent in the same 

 species at different stages. It is the presence of these structures that gives the 

 ' sculptured ' or ' ringed ' appearance to the scales, but these terms, though 

 frequently applied, are misleading. 



The fibrous stratum is readily exposed by treating the scale ^vith a dilute 

 acid, when the scalelets are to a great extent dissolved off, or their remains easily 

 removed by scraping. The fibres are arranged in definite layers : (i.) a superficial 

 in which the bundles are concentric ; (ii.) a deep layer in which the individual 

 bundles interlace with one another at right angles, each set running diagonally to 

 the long axis of tbe scale. A third layer, the fibres of which foi-m an irregular 

 network, is possibly present, but it is much more difficult to demonstrate. This 

 fibrous stratum stains readily with any of the ordinary reagents. 



The scalelets, placed upon the upper surface of the fibrous stratum, are them- 

 selves covered with a delicate epidermis, which is likewise easily stained. They 

 consist of flattened, imbricated, calcareous plates. If the epidermis be gently 

 removed and the whole scale be placed for a few minutes in borax-carmine, the 

 scalelets become barely tinged with the stain, more particularly in the younger 

 stages. If, however, the latter be previously treated with an acid, they stain 

 rather more freely. This leads to the inference that in the earlier condition they 

 are more thoroughly calcified, or rather, perhaps, that in the later stages they 

 contain a larger amount of organic material, and thus stain somewhat more 

 readily. 



Between the radiating lines of scalelets the deeply stained fibrous stratum is 

 seen, resembling the spokes of a wheel. In an early stage, before the scalelets 

 become imbricated, the fibres may also be noticed as transverse bands passing 

 between the individual plates of a row. 



On examining a section of an undecalcified scale the scalelets are seen to be 



