Are these eggs fertilized? -- newbie needing help!

[Tall-esRaisin]

Sorry, I've never dealt with fertile eggs and need some help! I don't have a lot of details, but I'll try my best.

I have a 2 year old sebright bantam hen who has been sitting on about 15 eggs. Recently I went on a vacation so I wasn't able to collect her eggs everyday and I think they might be fertile from my bantam cochin rooster. I don't know how long she's been on them or how old the eggs are, but I did hold them under a flashlight. All of the eggs had a dark mass inside the eggs, taking up about 50% of it. I didn't see the eye of the chick, nor any blood vessels (dead or alive). Not seeing blood vessels made me wonder, so I tested store bought eggs and other non-fertile chicken and guinea eggs; all of which were completely clear of any dark mass, so I'm leaning on the fertile side. I have been watching YouTube videos and they look similar to fertile eggs. I'm thinking of letting her sit on the eggs for 5 more days and checking again under a flashlight, but I would really appreciate some advice as I've never hatched eggs! Thanks! If you have any questions, I may have an answer, sorry if this wasn't very clear!

 

[sourland]

You don't say how long she has been setting, but it sounds as if the eggs are developing.

 

[Tall-esRaisin]

You don't say how long she has been setting, but it sounds as if the eggs are developing.

I think she might be sitting on them for a week, maybe more. I believe they (eggs) weren't all there when she starting sitting on them, so it's been added to. I will try to get a picture of one under a flashlight later!

 

[Tall-esRaisin]

Still needing some help, but I took pictures of two of the eggs. Sorry for the quality, also the black dots are on the eggshell not inside.