I noticed that sometimes this kanji appears with a drop (making the primitives 'hole' and 'dog', and sometimes without a drop (making the primitives 'hole' and 'large'). Even on the Yamasa page (http://www.yamasa.cc/members/ocjs/kanjid...enDocument) it seems to show the drop on the actual Kanji character, but not when you write it. I'm assuming that the one with the drop is the 'printed version', and the one without the drop is the 'written' version. Does anyone know why this is the case? Should I always write it without the drop?

突 with a drop is the Chinese form of the character. In (modern) Japanese, it should always be dropless.

http://zhongwen.com/d/172/d240.htm

I don't see any drop on the character on that Yamasa page. Maybe your computer is configured to default to a Chinese font.

Ah, you're right. I noticed in Firefox the Yamasa page doesn't show the drop, but in Chrome it does. Thanks for the info!