. . . "Forming the structure of the new society within the shell of the old" is actually a phrase from the Preamble to the Constitution of the Industrial Workers of the World, with the "structure" in question mainly supposed to refer to rank-and-file-run radical industrial unionism. So whatever it ultimately means, it’s something that syndicalists of all sorts are very often committed to, and also not something that’s supposed to be "rather than" radical unionization. To further complicate things, the predominant ideas in the IWW are not mutualist, but many mutualists are members (including myself). So if the IWW is taken as a representative of syndicalist ideas (which I think is fair, at least as rough guide) there are many of us who think that syndicalist ideas about strategy (focusing on industrial unionization, radical solidarity, and developing capacity to withhold labor power and exercise worker control at the point of production) are not necessarily contradictory with mutualist ideals about what a worker-owned free society might look like.