MOLLUSCA. 
215 
also by aggression, the foot being differentiated into prehensile 
arms, and the locomotion partially delegated to other organs. 
The following synopsis of the classes is given : — 
Saccata. 
A. Ilolozoic or typic. 
Mouth opens anteriorly. 
B. riiytozoic or hemitypic. 
Mouth opens posteriorly. 
4. Physiological Publications, 
Aucapitaine, H. Note sur la suspension de la vie chez V Helios 
lactea du Sahara Algerien. Lue h la Societe deClimatologie 
Algerienne le 4 Novembre 1864. Gaz. Med. Alger. 1865, 
Jan. 5, p. 9. Reported by Letourneux in Rev. Zool. 1865, 
July, pp. 212-214. 
This snail revived aftet having been enclosed almost without air in a bottle 
for three years and a half ; the snail had been found on calcinated groimd 
heated to 50° C. in a part of the desert where it was said not to have rained 
for five years. 
Fischer, P. Production artificielle des Perles. Journ. Conch, 
xiii. pp. 64 & 65. 
Some remarks about the well-known art of the Chinese, of having little 
figures covered with nacreous substance by living Dipsas [^Bai'bald] plicaia^ 
Sol. 
E. Morse, in his ^ Observations on the Terrestrial Pulmonifera of Maine ^ 
(see p. 230), states that Physa heterostropha (Say) and Limnams clesidiosus 
(Say) were not quite dead, but showed still slight motion after having been 
excluded from the air for respectively seventeen and seven hours (pp. 41 & 43). 
5. Historical changes of Faunas, Importation and 
Acclimatization, 
Mr. Morse has noticed the difference in the observations made 
by Dr. J. W. Mighels in 1843 and by himself, as regards the 
occurrence of the same species in the same locality ; some, then 
abundant, were scarce now, and vice versd (Terr. Pulmonif. 
Maine, pp. 56-58). [The freshwater shells offer the most striking 
instances in this respect ; in Europe every practical collector 
knows that a species may be abundant in one year, and very 
scarce or entirely absent in the next, in the same locality]. 
Dr. Morch informs us, with regard to the statement noticed 
in Zool. Record, i. p. 193, that many live specimens of Cyclo- 
stoma elegans have been in the meantime found on the south- 
western coast of Jutland. The nearest locality where it is found 
is in Hessen, in the neighbourhood of Cassel. 
Sac open at anterior) 1. Cephalopoda. 
end 
Sac open at both ends 
Sac open at the pos- 
terior end 
2. Gastropoda. 
3. Lamellihranchia. 
4. Tunicata. 
Sac closed j| 
