Help, egg yolk still attached to chick?

[zoo2u]

I posted last night that i thought i had lost my two chicks that pipped. one is definitely dead but the other just hatched out, membrane seemed to be very hard to get through and there is a large yellowish/greenish goo still attached to baby chick's bum. Is this the yolk and will it reabsorb or is this going to be fatal? The other 16 hatched with no issues whatsoever so last night were the first problems i started encountering. i am assuming it is due to the duration and different hatch dates of all these chicks... any info is appreciated.