142 The Ottawa Naturalist. [November 



the distant waters of the Mediterranean Sea or in the tropical 

 zones of the Athintic and Pacific. None are recorded in British 

 or Norse seas, or in the Atlantic waters of Europe. A precisely 

 similar find was that of two species of Oncoea, which Dr. Sars to 

 his uncontrollable astonishment found to be identical with species 

 quite recently captured by Dr. Giesbrecht in the Bay of Naples, 

 and described in one of his last papers. A beautiful Copepod so 

 perfectly colourless and translucent as to be almost invisible when 

 swimmings in the water, Dr. Sars recognized as a Mormonilla—'A. 

 highly remarkable genus established by Dr. Giesbrecht, and ot 

 which only twa species are known. Both species, strange to say, 

 are strictly confined to tropical Pacific waters, south indeed of 

 the equator. Yet here we find in the remote polar seas, over 

 twelve thousand miles away, Arctic specimens which can hardly be 

 distinguished from the Tropical species. Dr. Sars would have con- 

 ferred upon the Arctic form the name bestowed by Dr. Giesbrecht 

 on the tropical form, "were it not" he says "that the great distance 

 between the occurrences seems to forbid such an identification." 

 Hardly less remarkable and of extreme interest" not to zoologists 

 alone, but to geologists and physiographers, is the fact that two 

 polar species of Amphipods * [Pseudalibrotus) brought back by 

 Nansen are closely allied to forms peculiar to the Caspian Sea. 

 It is hardly possible to conceive of a more erratic occurrence of 

 creatures practically identical, and the most reasonable explanation 

 is that already provided by the geologists' supposition, usually 

 accepted, viz : the tormer continuity of the Caspian and the Polar 

 seas. 



Many interesting lines of thought are suggested by these re- 

 markable results of Dr. Nansen's expedition. Either the species, 

 practically identical, have originated independently in widely separ- 

 ated localities, or they have been carried from one centre to re- 

 mote and isolated areas, and have left us representatives in the 

 intervening waters. In the case of the Copepoda there is this pro- 

 foundly significant point to be noticed that zoologists are agreed 

 upon their primitive and unspecialised character. The Copepoda 

 are regarded as generalised, indeed the whole sub-class Entomos- 

 traca is looked upon as resembling the ancestors of the modern 

 * The common fresh-water shrimp {Gamniarns) is a typical Amphipod. 



