Roots: Darwin's The Voyage of the Beagle and On the Origin of Species plus his own diaries; Almost Like A Whale by Steve Jones. The Doctor reads from Herman Melville's The Encantadas (a sequence of descriptive sketches of the Galapagos islands recalled from Melville's view of them during his sea bound youth, as well as reading Darwin's former work)

Fluffs: Everyone pronounces Tulok's name as 'TU-lok', except Colin Baker, who prefers 'Tu-LOK'

Goofs: The Silurian bacteria will wipe out all but the newborn humans, which Tulok says the Silurians will enslave. But how does he expect the newborns will survive the days between the death of the adults and the take-over of the Silurians?

Shvak changes gender.

Technobabble: The Doctor carries a sonic emission detector, which proves handy locating homing devices.

Double Entendres: 'Perhaps they aren't quite so irresistible as they think they are?'

'After he saw them he started acting strangely'

Dialogue Disasters: 'I have your mind in my grasp!'

'You mean you're with us, lizard?'

Dialogue Triumphs: 'It's a sonic emission detector' '-What does it do?' 'It detects sonic emissions!''

The Doctor on history: 'Try to see it from my view... All of human life - just a brief candle in the darkness'

'I wouldn't trust him if he said the world's oceans were 'a bit on the wet side''

Evelyn on a Galapagos tortoise: 'It smells like a physics undergraduate.'

And Colin Baker's ad lib '...which I suppose means that that is in fact a tortoise tortoise, and that's something else I've taught us!"

Continuity: According to the Doctor, Silurian cities stood 'over a million years ago', while 'hundreds of thousands of years ago' the reptiles co-existed in groups of clans alongside the original 'ape primitives' - Australopithecus [which would make the reptiles a very long-lived species]. As a lesser species, the hominids became the Silurians' primary livestock and food source (the Silurians' election to leave seaweed to feed the humans in this story would appear to concur with current theories that Australopithecus was a vegetarian). The Silurians' chief scientist Tulok used genetic engineering to improve the creatures' flavour, increase their breeding cycle and intelligence, thus in effect creating early Homo sapiens. Tampering with nature breaks the most sacred tenets of Silurian law. Brought to trial for his genetic crimes in the Silurian 'Justice Chamber', Tulok was exiled along with his creations to die in the wilderness [the suggestion here seems to be that these events took place after the Silurians' retreat underground. Tulok states at the time that the wasteland above has been uninhabitable for ten years, while the outside temperature is twenty degrees [Celcius?] below freezing]. Surviving to wreak his revenge, Tulok sabotaged the hibernation chambers of his race, destroying 'all but a dozen or so' hibernation chambers. To Evelyn the Silurian hibernation chambers resemble vast crypts with 'stone coffins'. They employ hydrogen fusion reactors as their power source.

The Silurian 'third eye' can be used to hypnotise and coerce humans via a link to the subject's 'primal mind', although this might be resisted by stronger wills. Their tools include a high-intensity heat device (cf 'The Sea Devils')

The sounds of Emilio's 'race memory' episode include chimpanzee screams.

'Monkton's Theorem' states that no intelligent species is likely to leave behind fossils.

Evelyn was never very good with boats, and once tried to read Moby Dick, but gave up 'before they even raised anchor'.

The Doctor can tell the difference between male and female Silurians (though audio doesn't reveal whether they're sexually dimorphic or not). He assumes the alias of 'Doctor Albert Einstein', with which he says he has "inveigled" himself into the scientific society. He always meant to 'pop back and give [Alfred Wallace] some moral support' (see: Links). Melville is his favourite author.

Links: 'Doctor Who and the Silurians', 'Warriors of the Deep', 'The Marian Conspiracy'

Location: The Galapagos Islands (including the settlement of Baquerizo Moreno), September 19, 1835.

The Bottom Line: 'I believe in Descent through Modification!'

There are some great performances here, in particular Colin Baker is in fine form. But the story seems to be more interested in filling in gaps, such as in why the Silurians didn't wake up, why there are no missing links in the fossil records, or Silurians in the fossil records for that matter. This is a shame as the important event of Evelyn meeting her hero is subsumed in favour of big speeches about the role of man and lizard in nature. But it's done with such style you almost forget the most admirable bit - the word 'evolution' is, quite properly, never used.