INTRODUCTION. XXXIX 



It was in the year 1823 that Mr. Vaughan Thompson, 

 whoso name is now identified with the discovery, follow- 

 ing up an observation made by Slabber, a Dutch natu- 

 ralist, as long ago as 1768, and published ten years after- 

 wards, established the remarkable fact that those ano- 

 malous forms which constituted the genus Zoea of Bosc, 

 itro nothing more than the early or larva condition of the 

 higher Crustacea. It will readily be imagined that no 

 small excitement was produced in the scientific world by 

 the announcement of a discovery which, followed up, as it 

 afterwards was, with equal intelligence and perseverance, 

 and with corresponding success, may claim for its author 

 a place amongst the few observers who, from a single 

 pin 'iiomenon, have been led to the establishment of gene- 

 ralisations and laws of the highest importance. 



Notwithstanding, however, the credit is due to Mr. 

 Thompson of having carried out the suggestion to its full 

 development, it was undoubtedly to the Dutch naturalist 

 that he was indebted for the ascertained fact that the 

 anomalous creatures on which Bosc afterwards founded 

 his genus Zoea pass by metamorphosis into a different 

 and a higher form. 



Before I proceed with the further history of this dis- 

 covery, I think it right to show the grounds of Slabber's 

 claim, which had been wholly overlooked as to its results, 

 and which, in consequence of an error arising from de- 

 ficient information, Mr. Thompson himself, in the first 

 place, much depreciated, without, as far as I am aware, 

 having afterwards taken any opportunity of correcting 

 the misapprehension. It was, then, in the year 1778 

 that Slabber published a small work, in which occurs 

 a description with figures of a new crustacean animal 



