198 



KNOWLEDGE. 



[Septbmbeb 1, 1898. 



the vivacious animals springing oat of the water and falling 

 into it again produce the strange effect. 



Now, albeit that these creatures are so incalculably 

 numerous, they had to wait long before attracting scientific 

 attention. In 1770 there was published at Copenhagen, 

 by J. E. Gunner, Doctor and Professor of Divinity, and 

 Bishop of Trondhjem, an account of " Some small, rare, 

 and mostly new, Norwegian sea-animals." Among these 

 was one to which Dr. Giesbrecht awards the distinction 

 of being the first of the marine free-swimming Copcpoda 

 that was ever described and figured. It is no little credit 

 to the bishop, under these circumstances, that not only is 

 his species clearly recognizable, but his description of it is 

 almost entirely free from error. It should not be forgotten 

 that " Cuf's magnifying glass," with which he examined 

 his specimens, was not precisely the same kind of instru- 

 ment which microscopists have at command in the present 

 day. The species is now known as Calamus finmarchkus 

 (Gunner), and is sometimes spoken of as " whale-food." 

 That Gunner includes it among rare animals could only 

 have been in regard to its novelty, for he himself says, 

 that " Off Hammerfest, in West Finmark, the sea was 

 teeming everywhere with these minute animalcules, and 

 that a good number could be caught by merely letting the 

 sea-water flow into a bottle." So far from being really 

 rare, it happens that this is one of the four cosmopolitan 

 species, ranging from north to south, indifferent to heat 

 and cold. There are some four hundred* other species of 

 marine free-swimming Copepoda, of which a comparatively 

 few brace themselves exclusively with frigid waters, the 

 majority preferring their bath decidedly warm or at least 

 with the chill off. To the hardiest of the hardy must 

 those belong, which are capable not only of existing, but 

 of shining in the difficult situation which Nordenskiold has 

 described. " Very singular," he says, " is the impression 

 experienced in walking on a cold, dark, winter's day (with 

 the temperature nearly at the freezing point of mercury) 

 on snow from which on all sides shoot at every step 

 sparkles so vivid that sometimes one is almost afraid of 

 seeing one's boots and clothes catch fire." The sparkles 

 referred to in this passage emanate from living, though 

 not, under the circumstances, free-swimming Copcpoda. 



Without, however, tempting the perils of the sea, or 

 tramping over Arctic ice, the student, Uve where he may, 

 can rely on being able to obtain a fresh- water Cyclops from 

 the nearest pond. Little as it may seem to resemble crab 

 or cumacean, lobster orwoodlouse of the Malacostraca, 

 upon careful comparison the relationship will become 

 apparent. Examine the series of appendages. Observe 

 that the head, just as in the Amphipoda and Isopoda, is 

 supplied with two pairs of antennae and four pairs of 

 mouth organs. These latter are commonly spoken of as 

 mandibles, maxillfe, first maxillipeds, second maxillipeds ; 

 whereas in the Malacostraca we are accustomed to the 

 succession of mandibles, first maxill;?, second maxillae, 

 maxillipeds. The difference in naming came about in this 

 way. The celebrated naturalist, Professor Carl Claus, in 

 tracing the transformations experienced by young Copepoda, 

 found reason to believe that there was a loss of one pair 

 of maxilla, and, on the other hand, a severance of the 

 outer and inner branches of the maxillipeds to constitute 

 two distinct organs. Like the traditional origin of Eve 

 from Adam, this supposed making of two out of one has 

 not commended itself to all investigators. Dr. Giesbrecht 

 and Dr. H. J. Hansen agree in denying its validity, and, 



as Nature generally prefers the beaten track, there is a 

 presumption that they are right. It is in the hinder part 

 of the body, rather than in the front, that the Copepoda 

 differ from the Malacostraca. Following the mouth organs 

 are five, or occasionally only four, pairs of limbs, attached 

 to as many segments. The first four pairs almost always, 

 and the fifth pair often, are two branched. Then comes 

 the pleon, or tail-part, without appendages, but like the 



* More than forty of these were added in one batch from the Gulf 

 of Gruinea, by T. Scott, Eoq., r.L.s., in 1891. -See Trans. Linn. 

 Soc, London, Zool. See. 2, Vol. 6, Part 1, 



Figure of Cyclops serrnlatus Fischer. From Uljania. 



trunk consisting of five segments (the first two 

 usually coalescent in the female) and ending in the caudal 

 fork with its apical setae. 



In one division, comprising the families Calanidse and 

 Pontellidfe, there is a well-marked separation between the 

 trunk and the pleon. This division Giesbrecht calls the 

 Gymnoplea, Copepoda with footless pleon, as opposed to 

 the Podoplea, comprising the Cyclopidse, Harpacticidse, 

 Peltidiidffi and Corycaeidas. The Podoplea, meaning 

 Copepoda with foot-bearing pleon, have indeed a footless 

 pleon, like all the Copepoda, but here the constriction 

 between trunk and tail occurs after the fourth pair of limbs, 

 and by that means the fifth pair of trunk-Umbs, such as it 

 is, often a very small affair, lends its support to the pleon, 

 or tail-part of the animal. 



The Gymnoplea generally have a pulsating heart, almost 

 always lead a pelagic life, and have the joints of the 

 appendages in general more numerous and more variously 

 plumed than is the case in the Podoplea, The latter 

 scarcely ever have a pulsating dorsal vessel, and include, 

 besides numerous marine species, almost all that Uve in 

 fresh water. 



As these papers have the insidious object of tempting 



