On the GMAT, a COMMA + each modifier must serve to refer to the NEAREST PRECEDING PLURAL NOUN.
An OA from GMAC:
Deserts are inhabited by several distinct animal SPECIES, EACH with its own method of adapting to long periods of moisture shortage.
Here, COMMA + each serves to refers to species, the nearest preceding plural noun.
Conveyed meaning:
Deserts are inhabited by several distinct animal SPECIES, EACH SPECIES with its own method of adapting to long periods of moisture shortage.
Perhaps nowhere
...
An OA from GMAC:
Deserts are inhabited by several distinct animal SPECIES, EACH with its own method of adapting to long periods of moisture shortage.
Here, COMMA + each serves to refers to species, the nearest preceding plural noun.
Conveyed meaning:
Deserts are inhabited by several distinct animal SPECIES, EACH SPECIES with its own method of adapting to long periods of moisture shortage.
Perhaps nowhere
...
