582 
SUMMARY OF CURRENT RESEARCHES RELATING TO 
The retreat is proportionate to the time in which the Cephalopods are 
kept dark. Thus, what is true of Arthropods and Vertebrates is truo 
of Cephalopods also. Full details are promised. 
y. Gastropoda- 
Anatomy of Daudebardia and Testacella.* — Dr. L. Plate has in- 
vestigated five species of Testacella and two species of Daudebardia, but 
his memoir describing these also contains numerous observations on the 
comparative anatomy of other Opisthopneumatous Pulmonates. He 
signalizes the following as the three most important general results of 
his work. Many structural peculiarities of Testacella occur in less 
differentiated form in Daudebardia , the latter thus linking the Hyalina- 
and Testacella- types. The divergent position of the kidney and heart 
on the roof of the pulmonary chamber may be referred to two conditions, 
both associated with the carnivorous diet, to the displacement of the 
mantle-cavity to the hind end of the body, and to the formation of an 
air-reservoir in connection with the pulmonary chamber ; the Testacella- 
types are derived from prosopneumatous forms, their opisthopneumatous 
characteristic being secondarily acquired. The hypothesis of the 
diphyletic origin of the Pulmonata (von Ihering’s Branchiopneusta and 
Nephropneusta) is not reconcilable with the fact that the Testacella- 
types have in the hindmost corner of the pulmonary cavity a smelling 
organ obviously homologous with the sense-organ which Spengel has 
demonstrated in other Gastropods. 
Geographical Distribution of Slugs.f — Mr. T. D. A. Cockerell is 
of opinion that the “ Slugs ” are a polyphyletic group, and that five of 
the six constituent families are more nearly allied to as many testaceous 
groups than to one another. The families recognized are the Succineidse, 
the Vaginulidae, the Arionidse (allied to the Helicidac), the Limacidae 
(allied to the Zonitidae), the Testacellidae (allied to the Oleacinidae), and 
the Selenitidae. The paper gives only a detailed statement of facts. 
Larval Form of Parmophorus.J — M. L. Boutan discovered near 
Suez some small black masses a few millimetres in diameter ; these 
were Gastropods, the shell of which was partly covered by the lobes of 
the mantle ; he was fortunate enough to find a series of forms which 
led at last to the adult. The author has already shown that the larva 
of Fissurella passes through stages at which other generic types rest, 
and the present discovery confirms that view. 
5. liamellibranchiata. 
Lamellibranchiata.§ — Dr. P. Pelseneer treats very fully of this 
class, giving first details of descriptive auatomy, then a comparative 
anatomy of the organs under nine heads, and lastly discussing their 
relations to one another and to other Molluscs. He has convinced 
* Zool. Jahrb., iv. (1891) pp. 505-630 (6 pis.), 
f Proc. Zool. Soc. Lond., i891, pp. 214-26. 
t Comptes Rendus, cxiii. (189i) pp. 94-5. 
§ Arch, de Biol., xi. (1891) pp. 147-312 (18 pis.). 
