In spermatozoa of many animals, the Acrosome is an organelle that develops over the anterior half of the spermatozoon's head. It is a cap-like structure derived from the Golgi apparatus. Acrosome formation is completed during testicular maturation. In Eutherian mammals the acrosome contains digestive enzymes (including hyaluronidase and acrosin). 
- "acrosome definition - Dictionary - MSN Encarta". Retrieved 2007-08-15.