Particle Rapidity Density Saturation in Heavy Ion Collisions and the Dual String Model

We show that the Dual String Model with fusion leads, in heavy ion collisions, to strict saturation of the particle (pseudo-)rapidity density, normalised to the number of participant nucleons, as that number increases. Asymptotically, as the centre-of-mass energy goes to infinity with the number of participants fixed, this density approaches the nucleon-nucleon density. A comparison with recent WA98 data is presented.