Abstract
The hydrolyzing ratio (R) by enzymic digestion of the fibroin isolated from cocoon filaments was different hereditarily among silkworrh strains. Selection experiments on the R value was carried out for 2 or 3 generations successively by the inbreeding of moths producing cocoons giving high or low value. The R value and size of cocoons were significantly different between the high and low lines. Since the reelability was higher in the low line of R values, the determinatjon of R values can be usefull for a measure in selection experiments on reelability of cocoons.
