32 SUMMARY OF CURRENT RESEARCHES RELATING TO 



electric, plates or electroplaxes lying horizontally, separated by jelly- 

 like electric connective tissue. Inside the delicate bounding electro- 

 lemma of the electroplax the cytoplasm is arranged in three horizontal 

 layers — (a) the layer of electric nuclei, with peculiar rod-like or thread- 

 like objects running horizontally ; (b) a non-nucleated layer, with web- 

 like cytoplasm ; and (c) a dense cytoplasmic layer, with uniformly dis- 

 tributed nuclei, and with more distinctive striation than in any other 

 electric fish. 



Sense of Hearing in Fishes.* — Marage has experimented with carp, 

 tench, pike, eel, and other fishes, and finds no evidence of a sense of 

 hearing. The vibrations of synthetic vowels were transmitted into the 

 water immediately adjacent to the fishes, with an energy capable of 

 affecting deaf-mutes, but no results were visible. 



Sharks' Teeth and Cetacean Bones.f — C. R. Eastman discusses the 

 distribution of sharks' teeth and Cetticean bones on the ocean floor. 

 Teeth of Lamnidae and Carchariidje occur in all parts of the Pacific, l)ut 

 are much more plentiful in southern tropical regions than elsewhere. 

 Cetacean ear-bones are found only exceptionally north of the equator, 

 but are abundant south of it, especially between parallels 10° and 40° 

 south. Amongst Cetacean remains, those belonging to dolphins and 

 Ziphioids are the most common, and most widely distributed ; those 

 belonging to whalebone whales (rorquals) are unknown north of parallel 

 82° of south latitude ; and no indication of large sperm whales has been 

 found in any part of the Pacific, not even in those regions now frequented 

 by Physeteridas. 



On the last ' Albatross' Expedition (1904-1905) the largest haul of 

 sharks' teeth and Cetacean bones were made at stations lying within 

 the so-called barren regions, that is to say, areas far removed from the 

 land, beyond the reach of telluric food-supply, and characterised by a 

 most meagre pelagic fauna. The extent of these regions is sometimes 

 sugh as to constitute veritable death traps, comparable to deserts on 

 the land, for marine vertebrates that happen to have strayed therein. 

 Thus it is a significant fact that 70 p.c. of the entire amount of 

 material obtained during the last cruise of the ' Albatross ' was dredged 

 within the barren area. 



New Species of Pteridum. — L. "W. Byrne f describes Pteridum 

 alleni sp. n., captured at the mouth of the English Channel, near 

 La Chapelle Bank, at about 450 fathoms, on a recent cruise of the 

 S.S. ' Huxley,' employed by the Marine Biological Association in their 

 co-operation with the International Fishery Investigations. We note 

 this new species because hitherto only one species of Pteridum Scopoli, 

 as defined by Giinther,§ has been described, namely, Pteridum atrimi 

 Risso, a denizen of the Mediterranean coast of France, where, how- 

 ever, it appears to be uncommon. The distinctive peculiarities of this 

 new species are compared with those of P. atrum. 



* Comptes Bendus, cxliii. (1906) pp. 852-3. 



t Bull. Mus. Comp. Zool. Harvard, 1. (1906) pp. 75-98 (4 pis.). 



X Ann. Nat. Hist., xviii. (1906) pp. 448-50 (1 fig.). 



§ ' Challenger ' Deep-sea Fishes, p. 105. 



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