This section is from the book "Complete Self-Instructing Library Of Practical Photography", by J. B. Schriever. Also available from Amazon: Complete Self-Instructing Library Of Practical Photography.
Large Transparent Spots. These spots are generally caused by adding bromide to the developer while the plates are in the tray. A drop of bromide falling upon a plate while developing, will restrain that portion of the plate which the bromide has penetrated, consequently, a round transparent spot will result. Streaks and spots will be the result if the plate were allowed to lie in the bromide solution without rocking the tray.
SHEEP Study No. 5, See Page 344 W. E. Bertling, Buffalo, N. Y..