Originally published as a 4 story collection in 1959 and then with an extra fifth story at some point after1962. The Outward Urge is a history of the Troon family as humanity venture out into space.
This is the cover from the 1980's rejacketed collection of Wyndham novels published by Penguin. All covers were by Peter Lord and you either love them or hate them, I think. I remember picking this up in a bookshop in 1980/81 and disliking it. Odd because I really like it now and odder still because I actually own every other book in the set and bought all of them over the period of a couple of months yet somehow managed to forget all about this one with the passage of time. Just as well I like 2nd hand book shops and a good hunt, because it will be mine.