Final answer:
The twin walled, sac-like structure surrounding a cluster of capillary beds called the glomerulus is known as the Bowman's capsule.
Step-by-step explanation:
The twin walled, sac-like structure surrounding a cluster of capillary beds called the glomerulus is known as the Bowman's capsule. This structure is an important part of the nephron, which is the functional unit of the kidney responsible for filtering blood and producing urine.