Hi gunter, could you post the 3DM model file of your curves instead of only a screenshot? That then helps a lot to be able to use your own actual curves when answering your question.

It looks like you could give either sweep or network a try, but in order to do it you will first need to get the curves arranged so that your long main curve is not just one curve but is split into 2 separate halves (like Brian mentions above too). You can select it and use the Edit > Trim command to cut it - click the "Add trim points" button inside of Trim and then click on the curve at the spots to cut it at.

You would want to cut it at these spots here:



After you've cut it you should then have 2 separate curves, here I've shown them slightly moved apart so you can see how they are arranged:




With your curves then configured like that, you can select all the circles for the profiles, then run Sweep and select these 2 long curves as the rails for a 2-rail sweep. It should also work to select all the curves and run Network on them as well.

Check out here for another description of this method:
http://moi3d.com/forum/index.php?webtag=MOI&msg=415.2


Another possibility for building the main body part and then putting on rounded tips separately is by doing a revolve for the tips and then using Blend to connect the pieces together, check that out here:
http://moi3d.com/forum/index.php?webtag=MOI&msg=2221.5


And some other tips on blobular form modeling:
http://moi3d.com/forum/index.php?webtag=MOI&msg=4063.3


Often times these kinds of blobby all melty looking shapes can be done better in a sub-d modeling program rather than in MoI.

- Michael