ZOOLOGY AND BOTANY, MICROSCOPY, ETC. 39 



Marine Gastropods.* — Miss K. J. Bush publishes a useful revision 

 of the genera Gyclostrema, Adeorbis, Vitrinella, and related genera, giving 

 the original descriptions, and lists of the species belonging to the 

 different genera which occur round the coasts of eastern America. 



5. Lamellibranchiata 



Morphology of Teredo.t — Stanislaus Beuk published a brief but 

 well illustrated paper on this subject, with special reference to the 

 structure of ^the nephridia. From a comparative point of view, the 

 question as to the structures which are to be called siphons is of great 

 importance. The author uses the term for the two tubular prolonga- 

 tions of the posterior mantle border, beginning at the end of the gills, 

 and not for that region of the mantle which contains the gills and lies 

 between the siphons and the visceral sac. This latter region is repre- 

 sented in all Lamellibrauchs, but is usually short, while in Teredo it is 

 greatly elongated. The nephridia are as usual paired, are U-shaped, 

 and the right and left are completely separated. Each consists of a 

 funnel opening into the pericardium, and a nephridial sac followed by 

 a coiled region which opens into a tube directly continuous with the 

 ureter. The general orientation of the organs shows that Teredo is 

 the end of a series of forms of which Pholas is the most primitive. 

 The genera Pholadidea and Jouannetia are to be looked upon as inter- 

 mediate forms. 



Classification of Pectinidse.i — Mr. A. E. Verrill publishes a study 

 of this family with a revision of the genera and sub-genera. His 

 classification is based entirely upon the shells. An interesting intro- 

 duction is prefixed to the paper, discussing the value to the animal of 

 the usual modifications of the shell, and the relation of these to the 

 habitat,_i.e. to deep or shallow water. The author believes that the ribs 

 and marginal points of shallow water forms are important in enabling 

 these to resist wave action ; while in those from deep water strength is 

 sacrificed to a lightness which facilitates swimming. He believes that 

 the power of swimming was an early acquisition, possessed perhaps by 

 palaeozoic forms. 



Cardiac Rhythm of Pholas dactylus.§ — Prof. E. Dubois notes 

 that we have little precise information in regard to the movements of 

 the heart in molluscs. He placed a minute elder-pith index with a 

 long lever on the heart of Pholas, and got a tracing which shows that 

 the diastole is notably shorter than the systole, and that the pulsations 

 occur in groups of two or three separated by long intervals. The 

 operation involved cutting the median line of the mantle and separating 

 the valves of the shell. 



Development of Dreissensia.|| — Herr J. Meisenheimer has followed 

 this from the egg to the trochophore larva. The eggs liberated in the 



* Trans. Connecticut Acad., x. (1899) pp. 97-144 (2 pis. and 10 figs.). 

 t Arbeit. Zool. Inst. Univ. Wien, xi. (1899) pp. 269-88 (3 pi*, and 3 tigs.), 

 t Trans. Connecticut Acad., x. (1899) pp. 41-96 (6 } ls.).f 

 § Ann. Soc. Linn. Lyon. xlv. (1899) p. 83 (1 ii 



|| Habilitationschrift, Marburg, 1S99, 42 pp. and 1 pi. j Foiseliung&ber. Biol. 

 Stat. Plon, 1899, pp. 25-8. See Zool. Ceutralbl., vi. (1S99) pp. S '5-902 (4 figs.) 



