Hi, Mark Lewis!

 DM>>>> Correct, please: The cat, which walking by herself.
 ML>>> that looks like an incomplete sentence but if it isn't, i'd use
 ML>>> The cat was walking by itself. i used "itself" since we don't
 ML>>> know the sex of the cat... but if we do, then "himself" for male
 ML>>> or "herself" for female is OK...
 AK>> I thought that in English "cat" is male, like a ship is female.

 ML> no, cats are animals and animated objects... ships, cars, trains
 ML> are not animals and are inanimate objects...

But we can say about a ship:

Captain Blood, by Sabatini
-----Beginning of the citation-----
All day the Dutch brig was in sight, though by evening she had dwindled
to the merest speck on the northern horizon.
----- The end of the citation -----

 ML> but it depends on the context, too... there are instances
 ML> where "cat" may not be referencing an animal...

 ML> eg: that guy is a cool cat, man!

 AK>> "The cat, which walking by herself," is probably taken from a
 AK>> story for children, where they are told how the cat had become a
 AK>> domestic animal.

 ML> that's why i said it looked like an incomplete sentence... you have
 ML> two commas in your snippet whereas the original post had a comma
 ML> and ended in a period...

 AK>> The cat there could talk, and when the ancient woman invited him
 AK>> into the cave, he always replied, "I am a cat. I am walking alone
 AK>> and everywhere I want to." Do you have this story in the English
 AK>> literature?

 ML> not that i'm aware of but it has been a very long time since i read
 ML> any children's books...

As I have learned, the original story was written by Rudyard Kipling, "THE CAT
THAT WALKED BY HIMSELF"
http://www.boop.org/jan/justso/cat.htm

So he was male? 

We have a cartoon on this subject. 
https://www.youtube.com/watch?v=h2P_kWj8bJQ


Bye, Mark!
Alexander Koryagin
english_tutor 2019

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 * Origin: nntps://fidonews.mine.nu - Lake Ylo - Finland (2:221/6.0)