Quote Originally Posted by Shaggy
It does sound like fungus. I haven't removed fungus fom film in years(knock on wood) I seem to remember a commercial film cleaner that would do it. Edwal perhaps? Possibly Photographers formulary. They have an online catalog.
Best prevention is dry storage or dessicants.
Shaggy, thanks for confirming what I suspected. It'll take me time to get a photo cleaner but I've found a method - I'm not sure how permanent. I experimented with undiluted Photo-flo 200, dried the slides and then washed them in diluted Photo-flo solution. This seems to have done the trick. Sadhna.