goldfish anatomy?

1) What is the "plimsoll line" that I can see running down the side of
my common and the comet? a line of little dots down the scales, very
regular, running from the top of the gill to the middle of the tail?
(Not visible on the calico.)

2) Having read _far_ too much about goldfish diseases and symptoms, can
someone confirm that it is usual to be able to see very small
"capillaries" in the tail of a sarassa comet? the tail is almost
transparent, and I'm assuming it must need a blood supply - it's living
tissue, after all. these have been visible since I got the fish
(february).

the more you learn, the more you want to know!

thank you very much to anyone who can help.
--
sophie