Changes in Size: When a polymorph spell or effect changes its subject's size, DMs can decide that the size change does not stack with other effects that change the subject's size. For example, a human druid is a Medium creature. Our example druid uses the wild shape class ability to assume the form of a brown bear, which is a Large creature. The druid has used magic to gain one size category. The druid can't benefit from the enlarge person spell because the wild shape effect (which works just like the polymorph spell) changes the druid's creature type to animal (see previous section). As an animal (albeit temporarily), the druid could benefit from an animal growth spell, except that animal growth makes its subject only one size category bigger than normal and the wild shape effect already has increased the druid's size by that amount.
这个借口不错。。。
