ANIMAL LIFE IN THE SEA 181 



invertebrates do occur on the sea-floor in the greatest 

 depths, especially over regions covered by Globigerina 

 ooze. Among these invertebrates sponges and echino- 

 derms pr^onderate, molluscs and crabs among Crus- 

 tacea being rare. Of the sponges the old-fashioned 

 siliceous forms are numerous, and calcareous sponges 

 are absent. A few corals occur. Among the echino- 

 derms all the classes are represented, and the old- 

 fashioned crinoids, rare in shallow water, are relatively 

 abundant. Among the sea-urchins the special feature 

 is the abundance of old-fashioned irregular forms, which 

 occur so abundantly as fossils. Annelids occur especi- 

 ally in the red clay. In harmony Avith the great 

 uniformity of the conditions over wide areas, the 

 abyssal animals are widely distributed. Further, as 

 the conditions of temperature, and during the long 

 Arctic night the conditions regarding illumination, 

 show resemblance in polar and abyssal regions, there is 

 apparently some resemblance between polar animals 

 and abyssal animals. 



References. The forty- two volumes of the ' Challenger' Reports ( 1880- 

 91) give the resiilts of the epoch-making cruise of that vessel. More 

 popular accounts of its work are to be found in Mosely, Notes by a Natural- 

 ist ore the ' Challenger ' (London, 2nd ed., 1892), and WyviUe Thomson, 

 The Depths of the Sea (London, 1873), and Narrative of the Voyage of the 

 ' Challenger ' (London, 1885). The following may also be consulted : 

 Ortmann, Grundzuge der marinen TiergeograpMe (Jena, 1896) ; Chrm, 

 Aiis den Tiefen des Weltmeeres (Jena, 1900) ; Marshall, Die Tiefsee und 

 ihr Leben. For the more recent work discussed in the present chapter, 

 see Hjort, The ' Michael Sars ' North Atlantic Deep-sea Expedition (Geo- 

 graphical Journal, April and May, 1911) ; Hjort, Die erste Nordmeer- 

 fahrt des norwegischen Fischdampfers ' Michael Sars ' im Jahre 1900 

 {Petermann's Mitteilungen, IV, 1901), and The Depths of the Ocean, by 

 Sir John Murray and Dr. Johann Hjort (London, 1912). Two interesting 

 popular articles on the work of the Princesse Alice are Les Vertibris de 

 la Surface and La Faune PUagique des Invertebres, by Professor Bouvier 

 {Revue Oinlrale des Sciences, 1906). 



