You report on research in which “amputated specialist arms of male octopuses moved when in contact with progesterone” (Sex at arm’s length? Male octopuses use specialised arm to mate, scientists find, 2 April). How many octopuses were mutilated to discover this? Why? These are intelligent creatures that recognise themselves in a mirror, dream, understand deferred gratification, play, and recognise individual humans who interact with them. Why was this research procedure allowed? What overriding benefit could claim to justify it?
Pam Lunn
Kenilworth, Warwickshire

Last Wednesday’s Guardian print edition contained an advert for a model railway, based around a small branch-line goods train. A few weeks ago I bought a copy of the Times (the Guardian had sold out) with a more or less identical advert, but it had a much grander mainline Pullman passenger train. It seems clear what view Hornby has of the self-image of those who read the Times, but what should we make of its profiling of Guardian readers?
David Budgen
Durham

When I worked at the Eastman Dental Hospital and Institute some decades ago, I was widely addressed as “Uncle Prof” (Letters, 3 April). I was very happy about it.
Prof John Galloway
Croxley Green, Hertfordshire

Am I the only reader who was (until very recently) puzzled by the “alien facehugger” in your “Don’t miss a beat” subscription advert?
Christian Gould
Shepherds Bush, London

I’ve no problem with children in pubs (Letters 2, April). But I do have a problem with the parents who refuse to control them.
Rob Parrish
Starcross, Devon