210 PEOSE HAIilEIJTICS. 



mical differences, or any other, except difference of size) 

 often mistook one sort for another, |i,nd confounded half- 

 grown indi-sdduals of a larger with fall-grown individuals 

 of a smaller species. Such grounds for the separation 

 of mackerel into different species appearing to Scaliger 

 as wholly untenable, he came to the conclusion that all 

 mackerel are but varieties of the same fish; and that 

 those of the ocean are bigger than Mediterranean speci- 

 mens only because the ocean is bigger, and affords its 

 fish more scope for escape, and consequently more time 

 for development, or, as he neatly expresses it, ' In oceani 

 laxitate, fuga moram, mora parit incrementum; itaque 

 grandescere, quia non capiuntur.' The conjectures of the 

 ancients, however, as to diversity of species, have been 

 at length ftdly confirmed, and the doubts suggested by 

 Scaliger completely removed, by an interesting discovery, 

 which had escaped the penetrating eye of Aristotle, and 

 was first made by two French savans, so lately as the 

 beginning of the present century. In the year 1806, 

 Messrs. Biot and Delaioche ascertained that whilst some 

 mackerel, like our own, lack, others, like S. colias and 

 S. pneumatophorus, possess an air-bladder; and as this 

 singular difference in internal organization occurs in crea- 

 tures which are equally sportive and equally fleet, it 

 clearly establishes, first, the existence of at least two 

 quite distinct species of mackerel ; and proves inciden- 

 tally, in the second place, that this organ, so often de- 

 scribed as chiefly designed for assisting the locomotive 

 powers of fish, must answer some other end in their 

 economy, not hitherto clearly made out. 



Of the derivation of the Greek word cr/co/ti/S/jo?, no- 

 thing is certainly known. The Latin synonym lacertus, 

 or lizard, seems well selected to point out a fish like its 

 namesake on land in colour,* markings, and make, and 



* Pliny calls it stdpliur-colour, wliioli strange misuse of the 



