These particular blobs are actually Pectinatella magnifica a freshwater species of bryozoans or moss animals. They're colonies of tiny aquatic invertebrates with an extensive fossil record going back 500 million years.
The majority of bryozoan species are found in salt water. Each colony is made up of individual animals called zooids. They are filter feeders with tentacles for grabbing tiny protozoa and algae from the surrounding water. Some species give off chemicals that are being studied for use in medicine.
Amazing, fascinating creatures. Reminds me of "The Borg" from Star Trek. Intrigued and want to learn more? Visit these websites: http://www.bio.umass.edu/biology/conn.river/bryozoa.html and
http://www.wright.edu/~tim.wood/ (a professor studying freshwater bryozoans)
http://www.bryozoans.nl/index_en.html (gorgeous photos of freshwater bryozoans including species found in Europe)
http://www.micrographia.com/specbiol/bryoz/bryo/loph0100/pectindg.htm (This link has a great detailed black and white drawing of Pectinatella magnifica