C 8 7* 1 
Tull* who in a few days was fo obliging as to an- 
fwer my letter, and to fend me what I had requeued 
of him, and which I accordingly have tranfmitted to 
Mr. Trembley, for the Prince of Lichtendein. But as 
nothing of this fort has been communicated to the 
Royal Society, as a body, I thought it not improper 
to lay before you Mr. Tull’s account of his opera- 
tion j that, if it be thought worthy, it might be re- 
corded in the journals and regider-books of the So- 
ciety. 
In England, where in many parts fea-fifh are in 
great plenty, the fifh of rivers and ponds are lefs 
efteemed j and improvements, either with regard to 
their bulk or increafe, are lefs attended to : but in 
Germany, remote from the fea, where pond-fifh are 
a great article of traffic, Mr. Tull’s method may be 
of great ufe. 
Mr. Tull informs me, that he cadrates both the 
male and female fifh ; and that, although almoft any 
time is proper for the operation, the lead: fo is juft 
after they have fpawned, as the fifh then are too 
weak and languid to bear, with fuccefs, fo fevere 
an operation. The mod eligible time however is 
when the ovaries of the female have their ova in 
them, and when the vedels of the male, analogous 
to thefe, have their feminal matter in them ; inaf- 
much as at this time thefe vedels are more eafily 
didinguifhed from the ureters, which convey the 
urine from the kidneys into the bladder and are 
fituate near the feminal vedels on each fide of the 
fpine. Thefe may, without diffident attention, be 
taken for the ovaries ; and the more fo, when thefe 
lai are empty. When fifhejs have fpawned a few 
weeks,. 
