Who were the three dogs mentioned in the chapter who accompanied Buck on the boat ride north?

I don't see any actual names of dogs on the train. They would have been dogs like Buck being transported North to be sled dogs.

Again and again, as he looked at each brutal performance, the lesson was driven home to Buck: a man with a club was a lawgiver, a master to be obeyed, though not necessarily conciliated. Of this last Buck was never guilty, though he did see beaten dogs that fawned upon the man, and wagged their tails, and licked his hand. Also he saw one dog, that would neither conciliate nor obey, finally killed in the struggle for mastery. ch 1