I was sloppy with my mention of "quantum physics." I meant that the organism grows in quantal stages. I assume that once it decides to add a varix, it is commited to growing until the new varix abuts the prior one (a two-thirds turn). It probably can't stop half way, make a varix, and be in an viable form (for example, the new siphonal canal would stumble on the lastone). A snail with an indeterminate shell can just keep growing continuously; there are no decision points in the individual's development. It's interesting to ponder how the evolutionary leap was made from continuous, indeterminate growth to determinate growth of cowries and what I think of as the semi-determinate, fractal, quantal growth of cassids -- assuming that evolution proceeded in that direction. I collect lepidoptera, and I can see in conchology the same sort of variation on a theme -- with some fantastic outliers -- that makes looking at butterflies so appealling. Harry, thanks for supporting this little amateur investigation of mine. You all have a good thing going. Might be time for me to start a second collection! Brian (now a graphic/information designer in NYC, but once a biochem student) On Tue, 3 Apr 2012 11:09:44 -0400, Harry G. Lee <[log in to unmask]> wrote: >In nature, growth in /Cassis tuberosa/ seems to vary by no more than one >varix. > >The effect of environmental forces on maximal growth has been >demonstrated in species as diverse as/ Strombus gigas/ (mariculture; >dwarfism) and trematode-infected FW snails (gigantism). > >The heaviest of pelecypod ("bivalve") shells are sedentary (nowadays and >in the fossil record). > >I can't comment on the relevance of quantum physics. > >Harry > > >On 4/1/2012 10:37 PM, Brian Wu wrote: >> 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. >> ---------------------------------------------------------------------- >> >> >> > > >-- >Harry G. Lee MD >4132 Ortega Forest Drive >Jacksonville, FL 32210-5813 >USA >(904) 389 4049 >[log in to unmask] >[log in to unmask] > > ---------------------------------------------------------------------- [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. ----------------------------------------------------------------------