These beads are probably modern lampwork, but now I see the original concept that inspired the maker. Thank you.

Sometimes a similar effect was created using a pincer, so that two parallel indentations were made—and the desired effect of either undulating lines or swirls depended upon how much rotation was applied to the pincers.

The more-recent beads were made similarly. However, the glasswoker has cleverly inserted a pictorial mosaic-glass cane (as for millefiori work). In this instance, the process is pursued quickly (before this cane becomes too hot to be functional). The cane is inserted, twisted, and broken-off. Since the cane is broken, we can see it's cross-section—providing a small decorative unit. So the effect is similar, with the added bonus of providing a central decoration where the previous method left a depression.

JDA.