66 Zoological Society. 



circumstances concur, and without which those circumstances would 

 have no effect. 



Tlie chief aim of the present discourse was to point out the cir- 

 cumstances which bring about the presence of the same essential 

 cause in the cases of the development of the successive generations 

 completing the metagenetic cycle of the Aphis, the Medusa, the 

 Polype, and the Entozoon. The cause is the same in kind though 

 not in degree, and every successive generation, or series of sponta- 

 neous fissions, of the primary germ-cell must weaken the pollen-force 

 transmitted to such successive generations of cells. 



The force is exhausted in proportion to the complexity and living 

 powers of the organism developed from the primary germ-cell and 

 germ-mass. It is consequently longest retained and furthest trans- 

 mitted in the vegetable kingdom ; the zoophytes manifest it in the 

 next degree of force ; and the power of retained germ-cells to de- 

 velope a germ-mass and embryo by the remnant of the pollen-force 

 which they inherited, is finally lost, according to present knowledge, 

 in the class of Insecta and in the lower Mollusca. 



ZOOLOGICAL SOCIETY. 



June 11, 1850.— W. Spence, Esq., F.R.S., in the Chair. 



A Monograph of Scarabus, a genus of air-breathing 

 Gasteropodous Mollusca. By Arthur Adams, R.N., 



F.L.S. ETC. 



Scarabus, Montfort. 



Testa ovata, spira subohtusa, anfractibus compressis, varice utnn^ 

 que instructis ; apertura ovali inlus utrinque dentata ; peristo- 

 mate nan continuo, labro simplici, subexpanso. 

 The Scarabi have the eyes sessile on the inner bases of the ten- 

 tacles, which are short and annulated ; they live like most of the 

 other genera of Auriculiclce, in the damp woods and mangrove marshes. 

 None have been found in the African or American regions, but all the 

 species at present known are from the East Indies. 



Scarabus imbrium, Montfort, Conch. Syst. vol. i.; Ferussac, 

 Prodrome, p. 101 ; Chemnitz, Conch, vol. ix. pi. 136. fig. 1249 

 & 1250. 



Helix scarabseus, Linn. — Helix pythia. Mailer. — Bulimus scara- 

 baeus, Bruguiere. — Auricula scarabseus, Lamarck. 



S. testa ovato-prjranndali, rufo-fusco variegatd, longitudinallter 

 valde striatii ; spird acuminata ; aperturd subrotundatd, spiram 

 ce quant e ; labro postice injlexo. 



Hah. Island of Bohol, Philippines ; in dry woods, under stones, 

 and in earth ; H. C. (Mus. Cuming.) 



The large size, pyramidal form and strongly striated epidermis are 

 peculiar to this species : the upper tooth on the inner lip is more tri- 

 angular, and the posterior part of the outer lip is more inflexed than 

 in S, Lessoni. 



