AN IMAL- AiKNEU AL UKGAN IZATluN. 
|;J4 
Sykes, E. liuthven. — Note on Liiim:ea auricularia. — Journ. of Malac., 
vol. iii., |>p. 33 — 36, June, 1S!I4. 
Tate, U. — A Plain aiul Easy Account of the Land and Eresli\vatei\M(dlusks 
of ( treat Ihitain, Loudon, 1S6(). 
Tondin, J. 1!. P>.— Land Shells of Ilfracoinhe and neighhourhood.— Journ. 
of Conch., \ol. V., itp. LSI— 1N3, Apiil, 1SS7. 
Tryon, G. W.. jr. — Structural aiul Systematic Conchology, 188‘2. 
Tutt, J. W. — ^lelauism and iNIelauochroisni in r>ritish Lepidoi)tera, 
London, Oct., 18!)l, 8\'o, pp. 66. 
Tye, G. Sherrill'. — Notes on tlie Epidermis or Periostracuin of Mollusca. — 
Journ. of Conch., v., !»[>. 221 — 5, 1887. 
On the Periostracuin of Ileli.x arhustorum. — Conch., p. 53, Sept., 1892. 
Woodward, S. P. — A Manual of the INIollusca, . . . London, 1875. 
The Animal. 
The iiiollu.sk.s or animals, forming the sliells described in the fore- 
going iiages, liave soft, nnsegmented, and more or less bilaterally 
symmetrical bodies, whose e.xternal morphological features have been 
greatly changed by the e.xcessive development in size and moditica- 
tion in form of particnlar organs, or by their diminution or even 
total sipijiressimi and loss in mature life, 'i'he foot, the mantle, and 
the ctenidia or hranchia' have perhaps undergone the most remarkable 
changes, although the foot or podium has been comsidered to he the most 
permanent and di.stinctive nmlluscan organ, and its moditications very 
aiijiropriately used as the basis for forming the great divisions or 
classes into which the mollusca have been primarily separated. This 
enlargement or atrophy, as the ca.se may he, of the different organs of 
the body has caused a remarkably diverse and varied asiiect in the 
ditferent forms, hut these moditications are always correlated with 
and dependent upon the changes in and elaboration of their various 
and respective functions. 
A'otwith.stauding the great divergence in external shape brought 
about Ijy these moditications, the internal organization in the 
ditferent genera }>resents a rather striking nniformity in many iioints, 
and agree in po.s.sessing in common a number of .structural 
characteristics not found in other groups of animals. Being without 
an external or internal locomotory skeleton, the mollusca would seem 
to he more especially adapted for an aipiatic life, the locomotion 
of the terrestrial forms being limited and slow, although the different 
genera may he adajited to live under almost every variety of terrestrial 
and aipiatic conditions, and are capable of swimming, floating, 
burrowing, crawling and even spinning mucous filaments to facilitate 
locomotion when occasion reipiires their use. iSome species or groups 
