For fans who like to stick to earlier story titles, The Mutants poses a problem - for it is also the name of the first Dalek story. This is based on mentions in production paperwork back in 1964. To get round this they refer to this Pertwee story as The Mutants (1972) - i.e. they add the date.
The rest of fandom moved on and adopted the VHS / DVD nomenclature, so simply don't have this problem. The older story was The Daleks and this - and only this - is The Mutants. (By the logic of the more pedantic of the diehard fans, The Claws of Axos ought to be called "The Vampire from Space", as that was the title used by the production team. But it isn't).
Anyway, it's another mission from the Time Lords, which means yet again that they tell the Doctor nothing remotely useful that might help him carry out the mission effectively. If you want a parcel to get to where it is supposed to go, you put the name and address on it, do you not?
The sphere which the Doctor is given to deliver will only open for the person for whom it is intended, so he basically has to shove it against people to see who it responds to.
Trouble is, when it does finally get to its intended recipient - the rebellious young Ky - he hasn't a clue what the contents are, or what they mean. They are totally useless to him. It is only when the Doctor and the Earth scientist Sondergaard take a look at them that they start to make some sort of sense - so why was the Time Lord box not intended for Sondergaard in the first place?
If the tablets in the container are of vital importance to the evolution of the Solonians, what were the Time Lords doing with them in the first place? Talk about interference in the affairs of other races...
In the end, the tablets simply give them the information that Solos has very long seasons. It is the crystal in the cavern and the associated radiation which are the things which actually matter to the Solonians.
Sondergaard knows that the planet takes 2000 years to go round its sun, but hasn't figured out that this would mean very long seasons.
Why would an entire species become dependent on a single crystal for its evolutionary processes? Does life exist on Solos only within a couple of miles of the cave system?
There's also the question of how this race can forget such a Very Big Thing every 500 years, like clockwork.
And where does the next generation of human-like Solonians come from?
There is a teleport system set up between Skybase and Solos. It only appears to have a single station on the entire planet, right in the middle of nowhere. Not only that, but this vital link with the planet which the Marshal intends to dominate is never seen to be guarded. Anyone can walk in and use it.
The story is about racism and colonialism, so we get things like segregation. The Solonians have to use a separate teleport - but it's in the same building as the Overlords' one, in fact right next to it.
This lack of any form of security is especially odd when you consider that the humans believe there to be a deadly plague ravaging Solos.
Security within Skybase is just as bad. The only door that seems to have a working lock is the storeroom where the TARDIS materialises, which looks empty. The Marshal's office and the hydroponics areas can all be accessed by anyone, any time.
If the Marshal's office does have a working lock, wouldn't it have been sensible to use it before gunning down Varan's son just before daddy walks in on you?
Varan thinks pushing a chair aside to be an effective means of escape from the Marshal's office.
Did Christopher Barry really not twig that calling a Black character "Cotton" might jar, in a story that's supposed to be about race and colonialism? He was responsible for casting. The writers intended him to be a white Cockney character - hence his odd language, which wasn't changed to suit the West Indian actor cast.
Stubbs and he seem to switch sides very quickly. Varan's motivation is all over the place as well. One minute he's friendly to the Doctor for helping him escape Skybase, and the next he's throttling him, just because the cliff-hanger's due.
End of Part Two sees them fighting outside the teleport. Beginning of Part Three, they're in the teleport...
A later cliff-hanger is much worse for Varan, as his hand disappears due to shoddy CSO work.
This is the scene where an exterior wall has been blown open, and the warrior is sucked into space. For the others it looks as if there is just a bit of a strong breeze blowing, which they then just walk away from, now that the cliff-hanger is finished.
It's a good job that they opt to make the Marshal insane, as otherwise his scheming makes no sense at all. He clearly hates the planet and its people, so why so determined to hold on to it? A return to Earth and a nice office job should have been far more inviting than this. How does he intend to populate his "New Earth" if the natives are wiped out, with Skybase only having male staff and crew?
Why does he go to such lengths to fool the Earth Investigator, if he's simply going to lock him and his guards up and force them to live on Solos anyway?
Bob Baker and Dave Martin liked to do a lot of research for their stories, including scientific research. Yet they seem to think that "particle reversal" is the same as time travel - i..e. that it will put things back the way they were, rather than turn things inside out as the phrase is used to mean in other parts of the story. The Bristol Boys wrote two stories set in nuclear power stations, yet they don't seem to understand the way radiation works at all. Sondergaard dons a protective suit when visiting the cavern, yet later the radioactive crystal is handled by him and the Doctor without any form of protection. We know that the Doctor is only ever harmed by radiation when there's a regeneration in the offing, but Sondergaard should have been harmed by it. Later, its radiation seems to pour into Ky to help him evolve into Super-Ky. Why did it not do this with the Mutants in the cave system earlier?
To replicate the effects of earth tremors, director Barry employs the old Mirrorlon trick. You point your camera at this flexible mirrored material then poke it from behind so that it wobbles. It's been the way in which Ice Warriors kill people since 1967. Unfortunately he decides to film some other non-earthquake scenes in the laboratory bounced off Mirrorlon, making them look distorted.
There's a very rare Pertwee fluff, when he accidentally says "I couldn't even if I wanted to..." twice in the same sentence in the UNIT lab scene.
Finally - that hirsute old man rushing towards the camera in the opening shot. When they do the commentary on the DVD, the assembled team go "It's...!" as in the opening of any Monty Python episode. Surely Barry should have noticed this at the time.