CHAPTER XI. 



LINEAR SERIES continued. 



.M [>< HLLANEOUS EXAMPLES. 



Ix this chapter are given some miscellaneous examples. Most 

 of them illustrate the Meristic Variation of parts standing in 

 bilateral synnnrtry on either side of a median line. 



Here also are included certain cases of Variation concerning 

 the series of apertures in the shell of Haliotis, though probably 

 they are of a wholly different nature. 



SCALES. 



Among animals possessing an exoskeleton composed of scales, 

 the number of the scales or of the rows of scales found in par- 

 ticular regions is usually more or less definite. So constant are 

 these numbers in their range of Variation that in both Reptiles 

 and Fishes either actual numbers or certain ranges of numbers are 

 made use of li>r purposes of classification, 



Considerable Variation in these numbers is nevertheless well 

 known, and many instances are given in works dealing with 

 Keptiles or Fishes. The following cases are given as illustrations 

 of soim of the larger changes which may occur. 



403*. Clupea pilchardus (the common Pilchard). Among the 

 Pilchards brought to the curing factories at Mevagissey, Corn- 

 wall, specimens have from time to time been found by Mr Mathias 

 Dunn, the director, having the scales of one side very many more 

 in number than those of the other side. Two specimens 1 shewing 

 this abnormality were given to me by .Mr Dunn in IMS!). Owing 

 to the fact that the fresh Pilchards are shovelled wholesale into 

 the brine-vats, it is not until the fish are picked over for packing 

 after the salting process that any individual peculiarities are 



1 Tin - .-]irrmi. ns ;uv iinw in tin- Mnsi'uni of the Koyal College of Surgeons. 

 An account of tlinn \v;is puMi^icd in /'. /. ,S., Is90, p. 586. Figures of the same 

 variation were given by DAY, ., P. Z. .S'., 1887, p. 129, PI. xv. 



