This batch was much more successful than the earlier one. I didn't use perlite as the top layer, so there was less drying out.
I used only vermiculite in this pot. This was to see whether roots would develop more than in a perlite/vermiculite layered pot.
This produced at least one seedling with goodish roots.
Now repotted as:
There was a problem again with one of the taller seedlings, where the roots were poor and the seedling needed support.
And this one, large and healthy but poorish roots. However, the seedling had got entangled with three others, and I may have torn some root while disengaging it.
These are the three others - or four in fact!
I made an error while sowing, putting two seeds in one hole. You can see that the image bottom right is actually two cacti. The smaller one turned out to have no roots so I threw it away.
The larger seedling looks healthy and stood up easily without support.
I've repotted the remaining two with a seedling from the remaining batch of Cactus E (from Pot 33, see next report).
The alien cactus is bottom right in the first picture, out of focus.
The alien cactus, germinating in a pot of layered vermiculite/perlite, has a much better root formation than the cacti in the pure vermiculite pot. If this is repeated with other cacti (I haven't yet looked) rather than being a one-off, it would show clearly that layering works better.