Grammatically Correct: The writer's essential guide to punctuation ...

DON)T INCLUDE A PERIOD FORA GRAMMATICALLY
COMPLETE PARENTHESIZED SENTENCE THAT
LIES WITHIN ANOTHER SENTENCE
PUNCTUATION
Hospital workers objected that the consultant's advice on business
techniques didn't apply in their environment (for example, they felt
that telling desperately sick patients to "have a nice day" was
inappropriate) and was undermining rathPr than improving morale.
The foreign ministry said that five more diplomats would be expelled
(two had been ordered out of the country the week before), and
that a full investigation into the activities at the embassy would be
launched.
This also means that parenthesized text that lies within a sentence
cannot consist of two or more grammatically complete sentences
separated by a period. If you want to include a parenthesized comment
that contains two discrete points, you must join these points
with a colon, semicolon, dash or conjunction.
No: We trudged gloomily along the trail (the weather was damp and
miserable. We were also being eaten alive by mosquitoes) and looked
for a suitable site to pitch the tent.
Yes: We trudged gloomily along the trail (the weather was damp and
miserable, and we were being eaten alive by mosquitoes) and looked
for a suitable site to pitch the tent.
A stand-alone parenthesized sentence, of course, does take a
period. See the section on style conventions for "Parentheses" on
page 150.
USE A COMMA RATHER THAN A PERIOD TO END A SENTENCE
IN DIALOGUE WHEN MORE TEXT FOLLOWS
"I'm sure no one in the audience noticed when your toupee slid off," she
said soothingly.
"I realize you didn't blow up the house on purpose," he said plaintively.
"But it's undeniably rather inconveniencing."
For other aspects of punctuation in dialogue, see the appropriate
sections under "Comma," page 83, and "Quotation Marks," page 172.
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