lot 
MONSTROSITIES. 
irregularity in tlie secretive power of the animal, and the correlation 
which douhtless inseparaldy exists lietween the form and character of 
the shell and the organs of the Ixjdy renders it very probable that 
abnormality generally, indicates or is associated with, such functional 
disturbances or ilifferences as are detrimental to the creature and 
tend to its more easy destruction by its enemies, or by any unfavour- 
able couditious to which it may be exposed. The researches of Mr. 
K. ]'l. Call upon the relative abundance or rarity of the sinistral 
monstrosity of Mi-Idiitho in the embryonal and the adult stages are 
very signiticant, and show that the mortality amongst the sinistral 
specimens is strikingly greater than amongst those normally coiled, 
and would appear to corroborate the i)resuuied general physiological 
weakue.ss of abnormal specimens. It is, however, sometimes difficult 
to di.scrimiuate between a true variation and a monstrosity, but 
malformations or monstrous growths seldom occur in the embryonal 
stages, and an exaniination of the nucleus of the shell, whether 
ruivalve or Ihvalve, generally offers a clue to distinguish these 
accidentally malformed shells, as they frequently only develop the 
abnormality after the commencement of a free life — in fact, monstrosi- 
ties generally may be considered to l)e the more extreme examples of 
accidental variation, and their study is n.sefnl as tending to elucidate 
the range of specitic variability. 
rnhealthy or unnatural conditions of life would appear to dis- 
orgaiii/.e the animal functions, with the elfect that the resultant 
growth is often irregular or abnormal in appearance and character. 
A stream of water pumped I'rom a colliery at Leventhorpe Pastures, 
I- H,. :;i7. Kk,. 2t,S. 21!), iMG. 220. 
P/(inoH>is tayinalus Mull, (enlarged), 
I’il stream. Leveiultorpe I’asUircs, Leeds, culleetcd by Mr. Jas. Heevers, 
1 Jor.sal atid bide views <jf two individuals sliowinji the grotcsiiiie and irregular coiling assumed 
to be the elleel of abnormal eondilions. 
near Leeds, yielded a very large number of curiously twisted shells 
of !*!(( nurhis fdr/idtfti.'t, of which a large proportion were sinistrally 
coiled, and all of which were thickly encrusted with a dense black 
carljonaceous deposit. So universally i)revalent were these remarkable 
shells in this stream, that at one time it was a rarity to obtain a 
normally coiled .specimen. 
