Notes and Quef'ies. 



327 



the scales are formed, can be separated with a 

 delicate penknifi^ ; and by means of these 

 laminae, according to some authorities, the age 

 of a fish can be easily ascertained, each layer 

 representing one year's growth. The cycloid 

 scales are smooth, horny, bf)ny — such scales as 

 one finds on the herring, salmon, roach, etc. 

 The stenoid scales are serrated or spinous at 

 the exterior margin — such are the scales of 

 perch. In the granoid class, the scale is regu- 

 larly covered with thick angular cells, com- 

 posed internally of bone and externally of 

 enamel. Most of these species are fossil. The 

 best known example of this class is the bony 

 pike of North America. In the placoid class 

 the skin is covered irregularly with layers or 

 small plates or points of enamel. It includes 

 all the cartilaginous fish of Cuvier except the 

 sturgeon. Examples may be mentioned, such 

 as sharks or rays. Some of this denomination 

 are also fossil. Here is a piece of skin from a 

 member of the shark family. The top portion 

 of the skin, or rather the scales, have been 

 ground down after staining. This is the true 

 shagreen, used years ago for covering books, 

 bags, etc. It is employed by the Japanese at 

 the present day for much of their beautiful 

 laquer work. 



The structure of the spines or spur-like 

 scales of the skate is curious. The larger of 

 them consist of a button-like base surmounted 

 by a sharp apex or point. The outer and lower 

 point of the base is opaque white ; the spine is 

 hollow. 



The heads of most fishes possess mucous 

 pore? and ducts, usually in greater number 

 than on any other part of the body ; and this 

 distribution is one of the most beautiful ar- 

 rangements of Nature. The mucous or slime 

 by which the scales of fish are, as it were, var- 

 nished or water proofed, be exuded from the 

 pores of the head, is necessarily carried back- 

 wards by the current, or, in still water, by the 

 progressive motion of the fish, thus spreading 

 itself over the whole surface of the body. This 

 lubricating fluid is most abundant in fish with 

 small scales. The mucous orifices are, as I 

 have stated, along the whole laterel line. Oc- 

 casionally tlie scales are covered entirely by a 

 soft, thick cuticle, so as to be detected only by 

 close examination. This mucous may well 

 serve as a provision to assist in preserving life 

 during the period of torpidity or hibernation, 

 and, generally, to withstand the influences of 

 water. 



The scales of fish are, primarily, defensive.' 

 That is their first raison- d'etre. Without 

 scales they would quickly succumb to animal 

 or vegetable parasites. And note this remark- 

 able pro\ ision of Nature— if one scale be lost 

 it is .supplied by a new growth precisely similar 

 to that which furnishes a second finger-nail 

 on the human hand, when the first one has 

 been damaged or destroyed. 



In this connection I should like to mention 

 the tench. Unfortunately, I have not a tench 

 scale to show you to-night ; but as regards this 

 "fresh-water physician," as he is so often 

 called, there is very strong reason to believe 

 that a fish which has a scale torn off does, by 

 rubbing his body against the medicinally slimy 

 sides of the tench, heal himself during the in- 

 terval which intervenes between the accident 

 and the new growth of the scale. The tench's 

 slime forms on the body of the wounded fish a 

 protective film, which— when it hardens, as it 

 quickly does— precisely resembles that gold- 

 beaters' skin without which our human surgical 

 dressings would be so often difticult or impos- 

 sible. In the absence of mucous, whether 

 yielded by the tench or by the injured fish itself; 

 parasitic growths quickly commence on the 

 ancient site of the lost scale, these being fol- 

 lowed by malignant ulcers, and finally death: 

 Roach about spawning time are usually rough 

 and deficient of a plentiful supply of mucous. 

 The roughness is caused by a loosening of the 

 scales. Soon after the deposition of the ova, 

 however, the roughness diminishes, and the 

 abundance of the mucous makes it very un- 

 pleasant to handle the fish at all. 



It scarcely admits of doubt that the circula- 

 tion of the blood in the minute capillaries plays 

 an important part as to the color and the change 

 of color in fishes' scales. It is for this reason 

 that the fish takes their hues from their sur- 

 roundings. I have here the pigment scales which 

 I have scraped from the scales of a bream. Let 

 me call your attention to the experiment of Mr. 

 Shaw. He puts two parrs into two earthenware 

 vessels, one white and the other black inside. In 

 four minutes they had gradually assumed a color 

 nearly resembling that of the earthenware. He 

 then exchanged the position of the two fish, and 

 the result uniformly followed that the fish al- 

 tered .their tints to match their surroundings. 



Beyond controversy, this mutability of color 

 is a device of Nature whereby the fish is pre- 

 served by being rendered less visible to its lynx- 

 eyed enerriies— just as the chameleon finds pro- 



