ns 
M(>NSTRO!?ITIES — SCALAIUFORMITY. 
discoid form bvit rarely, tlie surface of tlie pond was tliickly covered 
by a very dense growth of the Lcmna, but on the plant afterwards 
dying away, the scalarid specimens ceased to be produced, and the 
ordinary discoid shells only were to be found. 
Herr Clessin records that the same deformities are produced in 
various species by ponds filled with other water plants, or on the 
shores of lakes among and between stones. 
A further cause suggested is that, during the growth season, the 
water in the ditches or ponds iidiabited by these species is often 
nearly drietl up, and that the efforts of the creatures in forcing their 
way through the thick mud in which they are sometimes left par- 
tially imbedded, to again reach the Avater, may easily cause an 
alteration in the direction of the new growth, if at the time in 
proce.ss of formation. 
H. Roliiaen endeavoured to produce scalariform specimens of 
Helivcx, at will, by attaching plaster-of-Paris upon the penultimate 
whorl, near the suture or line of attachment of one whorl with 
another, but he was in a degree unsuccessful in the attempt, as the 
mollusk.s, after surmounting the obstacle jdaced on their line of 
growth, reverted to their normal manner of coiling, or produced only 
irregularly grown and deformed shells, ([uite dilferent from the sym- 
metrically and gracefully coiled scalariform shells naturally produced. 
'I'he result of the e.xperiment led M. Roliiaen to believe that scalari- 
formity in shells is owing to .some accidental modification in the 
animal, such as the permanent contraction or relaxation of certain 
muscles coidd produce. 
!• !(.. '2V>'h — J/tii.f ncifiora/is inon^l. utihi/ i- 
tornit: Taylor, 
Uallyshaniion, l)onc*j;al, 
(Mr. W. Swanslon’s collection), 
showing a naturally grown scalariform shell. 
Kkr 2GG . — Helix aspersa Miill., 
Reared by Mr. J. Madison, 
Showing an artificially produced scalari- 
fonn shell. 
IMr. J. Madison has also endeavoured to [)roduce these scalariform 
shells by similar means to those adopted by M. Rofliaen, and has been 
to a similar extent successful in inducing the desired scalarity, but 
hopes to have much more symmetrical, and finer results as he gains 
more experience in their treatment. 
