Protocol for cytostatic factor extract preparation for spindle assembly. The quality of the eggs is essential for good CSF extracts. Always sacrifice quantity for quality when trying to make functional extracts. Discard any batches of eggs that have "puff balls" or activated eggs that constitute more than 10% of the eggs. Use laid eggs and collect eggs at about 16 to 17 hours after priming with Progesterone (found in Pregnant Mare Serum Gonadotropin (PMSG)).