Harry, thanks very much for the excellent explanation of an amazing natural process. The final paragraph of your reply refers to the "final varix." Are you saying that the number of varices is predetermined (determinate)? That at some point the animal doesn't try to grow its shell any further because somehow it knows that it cannot because doing so would result in some insupportable imbalance between factors such as the volumes of the cavity and living tissue, locomotive power vs the mass of the shell, shell accretion potential, etc.? I intuit that snails with indeterminate growth hit some sort of mathematical limit in size, but that the demands of growing varicate shells are extreme and that there is some quantum physics of sorts at work. By the way, now that I have the vocabulary, I found another post on CONCH-L about intervarical specimens http://www.listserv.uga.edu/cgi-bin/wa?A2=ind0312d&L=conch-l&D=0&P=6166 and attributes their rarity (at least in some species) to collector bias. ---------------------------------------------------------------------- [log in to unmask] - a forum for informal discussions on molluscs To leave this list, click on the following web link: http://listserv.uga.edu/cgi-bin/wa?SUBED1=conch-l&A=1 Type your email address and name in the appropriate box and click leave the list. ----------------------------------------------------------------------