542 SUMMARY OF CURRENT RESEARCHES RELATING TO 



■of seals and penguins) obtained by the ' Discovery.' He communicates 

 notes on the larval form by G. Pfeffer, who refers it to CalUteuthis. 



S. Liamellibrancliiata. 



Malacological Fauna of African Lakes.* — R. Anthony and H. 

 Neuville find that the malacological fauna of the lakes Rodolphe, 

 Stephanie, and Marguerite is essentially fresh-water ; there are no 

 halolimnic forms as in lake Tanganyika, hence the authors find no 

 authority for the extension of the Tanganyika hypothesis to these 

 smaller lakes. 



Phylogeny of Lamellibranchs.t — G. A. Drew discusses this subject. 

 He concludes that ontogeny and the probable conditions that have 

 resulted in the complication of structure both seem to indicate that the 

 division of the Mollusca into Lamellibranchs and Gastropods took place 

 at an early time before the ancestors had attained much complexity of 

 structure. There seems to be no reason for believing that Lamellibranchs 

 ever had more complicated head machinery than they have at the present 

 time. If this is true, they probably have never needed ganglia more 

 Anteriorly than they now generally have. 



Anatomy of Giant Scallop.^ — G. A. Drew describes the circulatory 

 and nervous systems of Pecten tenuico status. Blood from the mantle is 

 returned immediately to the heart. Most of the blood from other por- 

 tions is carried to the kidneys, from which it passes to the gills and 

 thence to the heart. A portion may avoid the kidneys and go direct to 

 the gills. Blood seems to act both as blood and lymph. The cerebral 

 and pedal ganglia are small, and somewhat removed from their usual 

 positions. The visceral ganglia are very large and complicated in struc- 

 ture. The circumpalhal nerves and the branchial nerves have ganglion 

 cells throughout their length. The otocyst nerves originate directly 

 from the cerebral ganglia. 



Movements of Ensis directus Con.§ — G. A. Drew has studied the 

 habits of this razor-shell clam, which is abundant all along the eastern 

 coast of the United States. It is an active animal, it burrows rapidly, 

 and may also swim and leap. In burrowing, the foot is worked into the 

 mud, the end is then swelled into a knob, and by its sudden withdrawal 

 the shell is drawn to the position of the anchored end of the foot. 

 Simultaneous with these actions a strong jet of water is thrown from the 

 anterior end of the shell so that the mud is softened or even washed 

 away as the shell descends. By a similar ejection of water from the 

 anterior end of the shell the animal can swim backward by a series of 

 jerks. By sudden protrusion of the foot, or by bending and suddenly 

 straightening it, the animal is able to throw itself about on the bottom. 

 Such moverjients are generally rapidly repeated when once begun. 



* Comptes Rendus, cxliii. (1906) pp. 66-7. 



t Biol. Bull., xii. (1907) pp. 239-43. 



X Tom. cit., pp. 225-45 (7 pis.). § Tom. cit., pp. 127-40 (1 pi.). 



