Cancer flagnalis of Linnaus. 105 
of a rudder.” On the leaft difturbance, it ftarts in the manner of a 
{mall fifh, and endeavours to fecrete itfelf by diving into the foft mud. 
It changes its fkin at certain periods, as is evident from the exuviæ 
or floughs being frequently found in the water in which thefe ani- 
mals are kept. ! 
Linnzus, as appears by his defcription in the laft editich of the 
Fauna Suecica, had obferved this infe&t; but though he particularly 
. mentions the appearance of the ovarium in the female, he propofes 
a moft extraordinary doubt, whether it may not prove to be the 
larva of fome fpecies of Ephemera. ‘He alfo repeats the fame queftion 
in the Syftema Natura. 
'The only writer who has given a very ample defcription of the 
Cancer ftagnalis, is Schæffer, who has called it Apus pifciformis. 
He does not allow the parts on each fide to be genuine legs, but 
rather a fort of branchiæ; and as the animal has no other parts 
which can be called legs, he thercfore gave it the name of Apus. 
He has given a very good magnified view of the male infect, and 
figures of both male and female in their natural fize; but thefe 
figures feem to have been taken from {mall fpecimens, and are by 
no means calculated to give a clear idea of the elegant appearance of 
the animal itfelf. 
I alfo find it figured in the 57th volume of the Philofophical 
Tranfactions, for the year 1767 ; where it is alfo defcribed, but the 
figures are inaccurate. In the defcription it is very judicioufly ob- 
ferved, that fince they are furnifhed with ovaria replete with eges, it 
feems not probable that they fhould ever undergo a further change, 
but that they are in their perfect or ultimate ftate. 
- Schæffer, who is exact enough in his general defcription, had no 
opportunity of obferving the infect in its firft ftate, or immediately 
from the egg; it is therefore this part of its hiftory which was ftill 
wanting to complete the defcription of fo curious an animal. 
p In 
