You'd think it'd be difficult to put a lump of jelly into a jelly-bag. Wouldn't it all slip and slide? Not to mention squidge and squash,
Turns out it's actually extremely easy. If your jelly-bag is a hungry Comb Jelly and your jelly is a delicious Comb Jelly, they'll do it all by themselves!
Video: Alvaro Migotto
Such are the predatory ways of Beroid Ctenophores. They're shaped like a gelatinous bag with a huge opening at the top to serve as a cavernous mouth. Like other Ctenophores they swim around by waving rows of hair-like cilia, however, they also have bundles of yet more cilia lining their mouth to act as teeth. They can use these to bite chunks out of other Ctenophores.
When they don't swallow them whole, that is. They seem to prefer the 'swallow-whole method'. And why shouldn't they? They're a gelatinous bag eating a lump of jelly. It just slides right down! And since they're almost entirely transparent, we get to see the LIVING Comb Jelly get slowly digested even as it struggles for freedom.
Personally, I prefer my jellies to be frugivores. That way they can be filled with delicious strawberries.