There’s an interesting article on UnHerd today, about a book called The Hidden Half: How The World Conceals Its Secrets by Michael Blastland, which apparently examines how strange reality really is, and how little we sometimes know about it (or even how little know we know about what little we know).
Some highlights:
So what caused these differences if not genetics or environment? Answer: we don’t know. And most laypeople – myself included, before I’d read Blastland’s book – didn’t even know we didn’t know. You, like me, probably thought that the argument in science was between genes and environment; not between genes and environment and… this other thing. Yet this other thing – this hidden half, called “enigmatic variation” – doesn’t just apply to crayfish. As much as half of human variation can’t be accounted for, writes Blastland, by either genetic or environmental factors.
You all know by now, for instance, that economic forecasting isn’t hugely reliable; perhaps it seems obvious that that’s in the nature of the thing. Animal spirits, irrational exuberance and all that, right?
But economic reporting, it turns out, is just as dodgy. Not only do we not know what’s going to happen, we don’t know what did happen. ONS figures for the economy two or three years ago continue to be revised in light of what has followed – and are often subject to confidence margins that can make the difference between a boom and a recession (Blastland cites one where a fall in unemployment of 3,000 was sombrely reported with a confidence margin of +/-77,000 – i.e. the figure could be a rise of 74,000 rather than a fall of 3,000).
And then there’s the “replication crisis” in the social sciences, where results on which whole subsequent fields of research have been built turn out to be, literally, junk science. Again, as many as half of the accepted results in the whole of social science or medicine are feared to be unreliable or plain wrong. The experiments simply don’t replicate. Even medicines that we know work may only work for a tiny percentage of patients – and we can’t predict which ones and we don’t know why.
Read more at Even experts are ignorant – UnHerd
David's random ramblings 
It’s probably “ Horizontal Gene Transfer”
It doesn’t sound like an educated author
I’ll have to read the book to comment further, but from what other sources I can check, Marmorkrebs are indeed genetically uniform, and I find no mention of horizontal gene transfer in that context. See for instance https://archiv.ub.uni-heidelberg.de/volltextserver/22489/1/Falckenhayn_Cassandra_PhDThesis.pdf, https://www.nature.com/articles/s41684-018-0030-y and particularly https://link.springer.com/article/10.1007/s12038-015-9506-8, which examines the issue of stochastic developmental variation as an epigenetic source of variation.
I don’t need to research Horizontal Gene Transfer, but the author should have before making his statements
But horizontal gene transfer appears to be unrelated to the issue of Marmorkrebs, that’s precisely the point. Why should the author research it (if in fact they didn’t) when it’s irrelevant? Especially since you feel no need to research the matter yourself to support what appears to be little more than an off-the-cuff opinion with no evidentiary basis? To then use that opinion to claim, as you did, that the author was uneducated seems unfair and without basis itself.