192 BRITISH ENTOMOSTRACA. 



figures of the young at different stages of their growth ; 

 but after having watched them for about fifteen days, lie 

 likewise appears to have desisted from further inquiry. 



Notwithstanding this, Miillcr could not persuade him- 

 self that such dissimilar creatures could be the same 

 animal, and he has accordingly, without giving sufficient 

 credit to these illustrious men, or watching the hatching 

 and progress of the young himself, formed these imperfect 

 creatures into two distinct genera, which he has called 

 Nauplius and Amymone.* Ramdohr and Jurine, how- 

 ever, have both rectified this mistake, and fully corrobo- 

 rated the assertions of Leeuwenhoek and De Geer, by 

 following out the transformations in all their extent. 



The time occupied in this process varies nmcli accord- 

 ing to the season of the year and the temperature. This 

 latter I have found produces an amazing difference in the 

 duration of the period so occupied, and I have no doubt 

 also, from my own experiments, that the process has been re- 

 tarded or hastened, just as the vessel iuAvhich they have been 

 kept has been placed in a light or dark situation. Jurine 

 says, in the case of the Ct/clojjs quadricornis, this process 

 has always lasted twenty days ; and in a series of very care- 

 ful experiments which he made in February and March, 

 he found it extend to twenty-eight days. For the first 

 eight days they underwent little or no change ; between 

 the eighth and thirteenth, the body appeared a little more 

 elongated ; between the thirteenth and nineteenth, the 

 line of demarcation between this increase of length and 

 primitive size was traceable by a line of a brown colour, 

 and the insect had acquired a third pair of feet ; between 

 the nineteenth and twenty-fifth, no great change took 



* Entomost., pp. 39-48. It is stated by Latreille, and echoed by some 

 other writers, that the Amymone of Miiller is the young of the Cyclops, in 

 its earhest state, when it lias as yet only four legs, and that when it receives 

 the additional pair it tiieu l)ecomes the Nauplius. This is not correct. The 

 different species of the Amymone are the young of the C. minutus in different 

 stages, and of one or two marine species ; and never assume the form of the 

 Nauplius. The Nauphus (at least the Nauplius salttitori/is) is the young of 

 the Cyclops quadricornis, which at its earliest stage resembles fig. 3 of jilate 1 

 of Miiller. Tlie Nauplius hraclealvs I have never seen, and do not know. 



