Again, we do not have to agree, I do not have to be right. I do believe I am, or at least close. But its not about right. Its about learning.
I do not disagree with your experiences. Not in the least. I have had many similar things occur. Including the lack of an embryo or a system of veins.
Let me step out of the snake box. I recieved these same hints as you, from kingsnakes, but I did not put two and two together until I ventured to other kinds of reptiles.
Lets start there. Kingsnake eggs are simple, fast, and somewhat predictable. Kingsnakes are easy, they are not very critical. After I left the kingsnake world. People told me I could not do to pythons what I did with kingsnakes, you know, breed them regularly, multiclutch them regularly, and allow normal successful reproduction within a year or a year and a half. Being the bonehead that I am, I stated pythons should be far easier then kingsnakes. They are. My reasons were, they are bigger, therefore much harder to kill. They indeed tolerate errors much better then kingsnakes that tolerate errors much better then little tiny snakes.
So I got pythons and worked with them. Low and behold, I was wrong, they were easier then I thought. I produced carpets, they hatched before the female was 18 months. I bred Whitelips with no problems, people thought they were hard. Then I attacked Blackheaded pythons and Womas(just big kingsnakes) And had no problem keeping breeding and breeding at a young age. While I did get two clutches in less then a year, they did not double clutch. But they did have huge clutches, I had clutches of 22 from both types. At the time, Blackheadeds only were suppose to have 6 eggs. This was in the very early 80's.
Why I mention this is, everything was about the same and clear, except for one thing. Blackheadeds and Womas, were critical nesters, if they did not have a suitable nest, problems occurred. The problems were, the perfect eggs did not hatch. But there were hints, pythons incubate their eggs. The females would not wrap the dead eggs and incubate them. They would search thru the eggs and recognize the live eggs and wrap and incubate them. Once I recognized what this was a nesting problem, and I allowed better nesting(no lite to start with) the problem went away. At the time other people were having fits, messing with incubation methods hanging them in baskets, over water, all sort of things. I remembered I hatched my first clutch of Blackheadeds eggs, stuffed in gallon jars on vermiculite, and they all hatched. Was I lucky or was hatching methods not the problem. I know I am not that lucky, so I figured out why. This occurs to this day with monitors. People are going all stupid over incubation techniques when thats not the problem. As you mentioned, good eggs are easy to hatch. But now good eggs means they have to be alive, not only fertile.
Then came monitors and monitors have some problems that will make all this clear. With snakes, at the time of laying, there is embryonic development, so there is normally something to candle. But with monitors and torts and some turtles and terrapins, there is this little thing called diapause. A pause in egg development. Well, monitors are king at this and can do both early and late stage diapause.
What this taught me was eggs can clearly be alive and fertile and have no visable development what so ever. They can do this for many months. Then all of a sudden act like normal eggs, swelling up, developing veins and progressing like kingsnake eggs. With this in mind, your example of eggs without development, that later hatched, answers my question about candling, you are not going to throw out eggs because they do not contain veins, are you. You already know better. If the egg is not rotten, your going to keep it. Yea? So candling is of no value, yea?
Also, monitors were expert at laying good eggs that never hatched. Heck just go the the KS monitor forum, people get eggs all the time, but very very few ever hatch. Monitors are not seasonal breeders, they are food and nest induced breeders. Like a bird. Many birds were not captive bred until someone recognized that they needed nests before they bred, then all of a sudden species that were not bred, produced like flys, when gave proper nests.
Monitors are also like snakes on speed, that is, they do the same things just a whole lot faster and more of it. For instance, the smaller monitors can go from egg to egg in four or five months. The larger ones in a year. We have had them produce up to 14 clutches(very small species) in a year. Even the larger species can and do have four or five clutches in a year, without problem. Heck, I have a medium female thats gravid on her 56th clutch, she will be nine in a few months. Why I bring this up is, they are speed teachers, you have many more events in a much quicker time period. You also get experience year-a-round. So you learn about eggs.
With some monitors, we have had, individuals from one clutch hatch, grow up and reproduce, before all the eggs in their clutch hatched. Hmmmmmmmmmmmmm holy stinky carp batman! In a lacie clutch, a third clutch, one individual hatched in 3 1/2 months, and the last in that clutch took one week shy of a year(51 weeks) With a cross clutch, we had some individuals hatch in the somewhat normal 6 to 7 months, but the last three broke the year barrier, the longest was 1 year 5 weeks.
If you want to go farther, lets talk about turtle and tort eggs, they are even goofier, more goofy, goofyist.
Why I bring this up is, they are all reptile eggs, do contain common traits. Problems and occurances from one type help you understand the other types.
So after years being away from kingsnakes, revisiting them and applying new information was lots of fun. It somehow worked well, as a small example, last year, we had a number of clutches, as a tiny experiment, we nested half and did not nest the other half, you guessed it, the proper nested ones hatched, the non nesters did not, even thought they appeared normal and fertile. Keep in mind, the adults were kept alike and the only difference was the nesting.
I had already understood the good appearing eggs not hatching, but it was fun to do a little test. So, with experience from other types of reptiles, the eggs without development are not a mystery. They either suspended development, or died upon fertilization. Or and this last one is questionable, for some reason, the eggs appeared alive to the females body and were treated like fertile eggs. You see, it seems the females body recognizes fertilized eggs and calcifys them but normally does not calcify infertile eggs. I do understand, this is not clearcut and for some reason, the females body does not recognize fertile eggs and does not calcify them. As you mentioned. I also had a bloodline of calkings that did not calcify eggs, ever. It was a learning experience to watch clear eggs develop and hatch. I would imagine the opposite could happen as well.
I also think your confusing this step with lack of calcium. Which manifests itself in depleteing of the skeleton, as in weakening of the spine, kinking of the spine, weakening and breaking of the ribs etc. Not in clear spots. I would imagine its more about the indoctorine system and a failure to produce hormones that promote the next step. Thanks FR
