We certainly do need to check our theories against reality to see if we need new theories, like the cutting edge stuff Mr. Barker mentions. The problem in this case may well be that few spider X spider or pin X pin breedings seem to have been done, or at least reported. I was wondering if anyone other than the founders of the two lines had ever done either but I did hear back from one other large breeder who had done spider X spider and its likely there are others this far in. But I've yet to hear much on detailed results. Spiders have been around long enough that even I have a pair now so eventually enough results should be available to start to figure out if the mutation is dominant or co-dominant.

If spider does turn out to be homozygous lethal (technically co-dominant I think) and predictable via standard genetics it would be very difficult to prove. Eggs often fail to hatch from non spider X spider clutches and het X het clutches often miss the homozygous. It's also very hard to prove something by its absence. Maybe we just haven’t been lucky enough to prove a homozygous spider yet. It would probably take detailed results from a lot of spider X spider clutchs to start to build a statistically significant trend. And then if it turns out that some how the homozygous embryos die before shelling (getting into the reproductive details I know almost nothing about) it would be even harder to prove with any certainty.

Getting back to pinstripe, this all goes double compared to spider because I believe there are even fewer pin X pin breedings and probably done by even fewer breeders (maybe for pinstripe it really is only the founder so far).