40 SUMMARY OF CURRENT RESEARCHES RELATING TO 



appears. The cerebral ganglia arise on each side of the apical invagina- 

 tion. The velar cells arise around the outer margins of the ganglia. 

 By the rapid growth of the anterior portion of the blastoderm these 

 organ bases are forced far apart and posteriorly until they come to lie in 

 the posterior margin of the blastoderm, and by a continuation of the 

 movement they are carried around to the ventral side of the embryo, 

 where the two halves of the organs approach each other and finally 

 unite in front of the mouth. The buccal ganglia have a somewhat 

 similar history. 



All other organs arise from the median posterior portion of the 

 blastoderm, and chiefly, if not entirely, from two " somatoblasts," 

 strikingly like the origin of post-oral organs in Annelids. 



All homologous organs arise from corresponding cleavage-cells in 

 Fulgur and Crepidula, and probably all other Gastropods. Great in- 

 crease of yolk does not modify the type of germinal localisation, though 

 it profoundly affects gastrulation and later stages. 



Structure of Californian Haliotidae.* — Clayton F. Palmer describes 

 the structure of Haliotis rufescms and H. cracherodii, devoting especial 

 attention to the kidneys, the two reno-pericardial canals, the circulation, 

 and the nervous system. 



Development of Lung in Ampullaria depressa.t, — B. McGlone 

 finds that the lung is a secondarily derived structure, arising as an 

 invagination of what would become a gill filament. The osphradium is 

 similarly a modified gill, and may be the homologue of a gill situated 

 on the left side. 



Structure and Relationships of Oncidium.:}: — W. Stantschinsky 

 gives an account of three new species of Oncidium from Queensland, 

 and discusses the systematic relationships of the members of this genus. 

 He finds that the sub-genus Oncis includes more primitive types, but 

 annectent forms unify the whole genus. The absence of dorsal eyes in 

 the species of Oncidium is due to secondary degeneration. Most of the 

 Oncidiidas are amphibious, sometimes living in the sea, sometimes on 

 the beach ; but some species seem to have left the water altogether, and 

 illustrate the influence of isolation in species-forming. 



8. Liamellibranchiata. 



Supplementary Siphon in Lutraria ellipticaj — R. Anthony de- 

 scribes a curious abnormality in this common bivalve, namely, the 

 occurrence of an extra siphon, arising apparently as a bud from the 

 dorsal wall of the expiratory siphon. A section shows an external 

 epithelium, a layer of circular muscle-fibres, a layer of longitudinal 

 muscle-fibres, a second layer of circular muscle-fibres, a second layer of 

 longitudinal muscle-fibres, a third layer of circular muscle-fibres, an 

 internal epithelium, and a narrow central cavity. In other words, it 

 has the normal structure of a siphon, but it ends blindly. 



* Proc. Acad. Nat. Sci. Philadelphia, 1907, pp. 396-407 (1 pi. and 4 figs.). 



t Johns Hopkins Univ. Circular, No. 3 (1907) pp. 176-9 (2 pis.). 



% Zool. Jahrb., xxv. (1907) pp. 353-402 (2 pis. and 3 figs.). 



§ Arch. Zool. Exper, vii. (1907) Notes et Revue, No. 3, pp. lxxxviii.-xcii. (5 figs.) 



