To find the mean number of kittens in the litters, we need to add up all the kittens and then divide by the total number of litters.
Total number of kittens = 3 + 4 + 5 + 6 + 6 + 4 + 3 + 6 + 5 = 42
Total number of litters = 9
Mean number of kittens = Total number of kittens / Total number of litters
Mean number of kittens = 42 / 9
Mean number of kittens = 4.67
Therefore, the mean number of kittens in the litters is 4.67.