These Puppies and kittens live very well together. The important thing to remember: you need to ensure the animals are calm and comfort, to make it clear to pupils that they are in no danger.
In any case, do not use the method of punishment — do not scold tailed for hostility or uncertainty, on the contrary, encourage them for good behavior and friendliness. For example, instead of yelling at the cat for hissing, praise her or treat her to something when she stops doing it.
As soon as he felt that the puppy and the kitten calmed down and pose no threat to each other, you can remove the leash, but still the first time should monitor their communication. Make sure that each of the Pets was a secluded place, where he could be alone, to hide.