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 preponderate, 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 with 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 results 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 on the ‘ Challenger’ (London, 2nd ed., 1892), and Wyville 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, Grundziige der marinen Tiergeographie (Jena, 1896); Chun, 
Aus den Tiefen des Weltmeeres (Jena, 1900); Marshall, Die Tiefsee und 
thr 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 Vertébrés de 
la Surface and La Faune Pélagique des Invertébrés, by Professor Bouvier 
(Revue Générale des Sciences, 1906). 
