“XX,” named after the chromosomes, is the first horror anthology written and directed entirely by women (not counting that one of the shorts is based on a Jack Ketchum story). That’s a worthy achievement, especially in a genre as male-dominated as horror, and it proves a previously untested theory: that women are just as capable of producing a hit-or-miss anthology as men are.

There are four shorts, arranged in what turns out to be ascending order of quality. Each has at least one element that’s great, and at least one element that’s disappointing. But the good outweighs the bad overall, and there’s a great deal of fiendish creativity on display — and hey, it’s only 80 minutes total.

In brief:

– “The Box,” by Jovanka Vuckovic (adapting Ketchum), is about a busy mother (Natalie Brown) whose son is shown something mysterious by a man on the subway and subsequently stops eating. The psychological infection, whatever it is, spreads to the boy’s sister and father, too. The acting in this segment is stilted and slow, and the sinister premise doesn’t pay off in the end. But there’s a moment of fantastic gore effects (in a dream sequence that should have been the actual ending, but never mind).

– “The Birthday Party” is a dark comedy starring the delightful Melanie Lynskey as a woman whose hated husband keels over dead just before their daughter’s birthday party, leading her to hide his body so as not to spoil the festivities. Directed by Annie Clark (aka singer St. Vincent) and written by Clark and Roxanne Benjamin, this one suffers from its thin premise, the presence of an inexplicably weird nanny character, and the fact that it leads to a single so-so punchline. It’s also a bit of a letdown that one-fourth of this horror anthology isn’t horror at all. But there are some laughs in it, plus: Melanie Lynskey!

– “Don’t Fall”: OK, now we’re talking! Written and directed by Roxanne Benjamin, this is slick meat-and-potatoes horror about two couples on a camping trip who encounter an ancient evil. It plays like the condensed version of any number of movies about people who go out into nature and get killed, with Benjamin hitting the right beats of tension, surprise, levity, and horror. But this one, too, doesn’t pay off. The story is fully resolved when the film ends; it just turns out not to have been much of a story, lacking all but the most basic details. Someone should give Benjamin the budget and resources to make a feature, though, because she clearly has the chops.

– “Her Only Living Son” comes from Karyn Kusama (“The Invitation,” “Girlfight,” “Jennifer’s Body”), the most experienced of the four directors and the best at her craft. Here we have another mother, Cora (Christina Kirk), whose son, Andy (Kyle Allen), is turning 18 and has been acting like a sociopath. Even more disturbing: authorities like the school principal give him a free pass, saying he’s “special” and worthy of all the leeway he needs. A mother coming to realize her child is a monster is one of the most unsettling premises there is, and Kusama builds the dread expertly — and then, again, things fizzle out.

This is approximately the trajectory most horror anthologies take: some good segments, some bad, none long enough to scuttle the whole thing. The only noteworthy difference between “XX” and the average male-directed anthology is that, wouldn’t you know it, there’s no rape or torture. Weird.

B- (1 hr., 20 min.; Not Rated, probably R for some profanity, some graphic violence and gore.)