MANUALS, ANATOMY AND PHYSIOLOGY. Moll, 11 
by a coloured geographical map. — A short recapitulation in J. de Conch, 
xxix. pp. 182-184. 
W. Kobelt has finished his popular treatise on Conchology, “ Illus- 
trirtes Conchylienbuch,” the last two parts containing the Bivalves and 
Brachiopods. 
The first part of vol. iii. of Tryon’s Manual of Conchology, containing 
the Tritonidoe and part of the Fusidce, 64 pp. 20 pis., was published in 1881. 
Aristotle’s observations on the Mollusca, chiefly their external and 
internal structure, are compiled and arranged in systematic order with the 
addition of some explanations by N. C. Apostolides & Yves Delage ; 
Arch. Z. exper. ix. pp. 405-420. [They think that Aristotle’s second 
genus of Nautilus cannot be any other than Nautilus pompilius, but they 
are certainly wrong in translating the Greek Aporrhais by Pterocera . — 
Reg.] 
Anatomy and Physiology. 
1 . General Morphology, 
E. Ray Lankester criticises some statements made by J. W. 
Spengel and W. K. Brooks concerning the general morphology and 
the development of the Mollusca^ with special regard to his own 
previous observations, and suggests that the contractile posterior append- 
age of the embryo of the slug is homologous to the yelk- sac of the 
Cephalopods, the latter being also rhythmically contracted at a very early 
period. Ann. N. H. (5) vii. pp. 432-437, woodcut. 
Critical remarks on this paper by J. W. Spengel as to his own obser- 
vations ; Zool. Anz. iv. pp. 435 & 436. 
2 . Muscular System and Movement, 
K. SiMROTii maintains his theory that locomotion in snails is effected 
by extension of the muscular fibres and periodical coagulation of their 
contents [see Zobl. Roc. xv. Moll. p. 8, and xvi. Moll. p. 13] ; the aquatic 
non-air-breathing snails progress 2-3 centimetres in a minute ; the 
aquatic air-breathers, whose body is specifically lighter from the air con- 
tained in the respiratory cavity, 7-8 centimetres in the same time. The 
progression of land snails is rendered more difficult by the greater weight 
of the same body in air than in water. Cyclostoma elegans overcomes 
the difficulty by lifting up one lateral half of the foot before it is 
extended forwards, thus avoiding the resistance caused by close contact 
with the soil, and by accessory fixation of the snout ; foot and snout are 
for that purpose moistened by the secretion of numerous mucous glands ; 
nevertheless the animal progresses scarcely one centimetre in a minute. 
The inoperculate land snails overcome the difficulties by having a well 
developed network of sympathic nerves which continue their action 
without direct influence of the will, creating a row of distinct waves in 
the sole, and by converting the gliding motion on the front of the foot 
into a rolling one; Limax is therefore able to progress 13-14 centi- 
