1^2 BRITISH ENTOMOSTRACA, 
figures of the young at different stages of their growth ; 
but after having watched them for about fifteen days, he 
likewise appears to have desisted from further inquiry. 
Notwithstanding this, Muller 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 much 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 ray own experiments, that the process has been re- 
tarded or hastened, just as the vessel in which they have been 
kept has been placed in a light or dark situation. Jurine 
says, in the case of the Cyclops 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 Muller is the young of the Cyclops, in 
its earliest state, when it has as yet only four legs, and that when it receives 
the additional pair it then becomes 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 Nauplius (at least the Nauplius saltatorius ) is the young of 
the Cyclops quadricornis , which at its earliest stage resembles fig. 3 of plate 1 
of Muller. The Nauplius bracteatus I have never seen, and do not know. 
