Timing on Narcomoeba

[Sextiger]

1. When Narcomoeba hits the graveyard, does it immediately come back into play or can you respond to its ability with say Tormod's Crypt?

2. Let's say I have a Tormod's Crypt out and my opponent is playing Ichorid.  He has two dredgers, on the first dredge he hits a Narcomoeba and then on the second dredge he hits another one.  Would the Narcomoebas come back at the same time or do come in after each dredge? 

[Binary]

Narcomoeba
1{U} (2), Creature - Illusion 1/1
Flying
When Narcomoeba is put into your graveyard from your library, you may put it into play.

1) The ability starts with the word "When," so it's a triggered ability and can be responded to just as any other (non-mana) triggered ability.

2) Since two triggered abilities can't resolve at the same time, each ability has to resolve separately. Assuming both dredges happened during the resolution of the same spell or ability (one whose effect involved multiple card draws), both abilities would go on the stack immediately after that spell or ability resolves, then both players would get priority.