Notices of Memoirs — Antarctic Exploration. 275 



" These statements with reference to shore-fishes might, with some 

 modifications, be repeated concerning the distribution and character 

 of all classes of marine invertebrates in high northern and high 

 southern latitudes. The 'Challenger' researches show that nearly 

 250 species taken in high southern latitudes occur also in the 

 northern hemisphere, but are not recorded from the tropical zone. 

 Fifty-four species of seaweeds have also been recorded as showing 

 a similar distribution.^ Bipolarity in the distribution of marine 

 organisms is a fact, however much naturalists may difi'er as to its 

 extent and the way in which it has originated. 



" All those animals which secrete large .quantities of carbonate of 

 lime greatly predominate in the tropics, such as Corals, Decapod. 

 Crustacea, Lamellibranchs, and Gasteropods. On the other hand, 

 those animals in which there is a feeble development of carbonate of 

 lime structures predominate in cold polar waters, such as Hydroida, 

 Holothurioidea, Annelida, Amphipoda, Isopoda, and Tunicata. This 

 difference is in direct relation with the temperature of the water in 

 which these organisms live, a much more rapid and abundant 

 precipitate of carbonate of lime being thrown down in warm than 

 in cold water by ammonium carbonate, one of the waste products of 

 organic activity. 



" In the Southern and Sub-Antarctic Ocean a large proportion 

 of the Echinoderms develop their young after a fashion which 

 precludes the possibility of a pelagic larval stage. The young are 

 reared within or upon the body of the parent, and have a kind 

 of commensal connection with her till they are large enough to take 

 care of themselves. A similar method of direct development has 

 been observed in eight or nine species of Echinoderms from the cold 

 waters of the northern hemisphere. On the other hand, in temperate 

 and tropical regions the development of a free-swimming larva is so 

 entirely the rule that it is usually described as the normal habit of 

 the Echinodermata. This similarity in the mode of development 

 between Arctic and Antarctic Echinoderms (and the contrast to what 

 takes place in the tropics) holds good also in other classes of 

 Invertebrates, and probably accounts for the absence of free- 

 swimming larvEe of benthonic animals in the surface gatherings in 

 Arctic and Antarctic waters. 



" What is urgently required with reference to the biological 

 problems here indicated is a fuller knowledge of the facts, and it 

 cannot be doubted that an Antarctic expedition would bring back 

 collections and observations of the greatest interest to all naturalists 

 and physiologists, and without such information it is impossible 

 to disciiss with success the present distribution of organisms over the 

 surface of the globe, or to form a true conception of the antecedent 

 conditions by which that distribution has been brought about." 



Dr. Murray concluded his paper as follows : — 



"There are many directions in which an Antarctic Expedition 

 would carry out important observations besides those already touched 



^ Murray and Barton, ' ' Phycological Memoirs of the British Museum, ' ' part iii ; 

 London, 1895. 



