Febrhart, 1902.] 



KNOWLEDGE. 



39 



fully-furuisheJ pvcnogonid with a- mtilacostracau uot fully 

 furnished. Yet to this couveuieut procedure he was led 

 probuMy less by his own aeuteness than by the odd 

 behaviour of some earlier naturalists. 



So long ago as \6To the little auiphipod, now known as 

 Cyamus ceti (Linn.), whieh nibbles the skin of the Green- 

 land whale, was described and rudely figured by one 

 Friderich Martens, who evidently had in him the making 

 of a good naturalist. Though vulgarly called a whale- 

 louse, the Cijamiis is as true a malacostracan as any crab 

 or lobster. But it has its own features of distinction. 

 Among the amphipods it belongs to that section called 

 Caprellidea, which have so little of the roving disposition 

 that they have found it convenient to disjjeuse with pleo- 

 puds or swimming feet. As a corollary to this act of 

 abnegation they have reduced the pleon (or abdomen), 

 which elsewhere carries the pleopods, to little more than a 

 vestigial stump or reminiscence. On its head Cijamus 

 carries a pair of simjde eves, and on its trunk or middle 

 body instead of the normal seven pairs of legs it has but 

 five paii"S. the third and fourth having dwindled away to 

 mere attachments for the branchiae and the female brood- 

 pouch. Now in 1 76b Job Baster, a Dutch enthusiast 

 on the botany and zoology of the day, called attention to 

 this Cyaiuiig in a singular manner. He was writing of 

 fish-lice, and after remarking on the horror which many 

 persons feel at the second half of that compound word, 

 he adds that " a naturalist, ou the other hand, who can 

 never think it undignified to examine what God has not 

 thought it undignified to create, finds tokens of the 

 divine wisdom, power, and providence, as well in the 

 desi)ised louse as in the great elephant or rhinoceros." 

 That is written in the spirit of a philosopher. But later 

 on he makes particular observations which became the 

 source of prolonged confusion. He describes and figures 

 a pycnogonid, for some inscrutable reason introducing it 

 as a whale-louse, though he does not pretend to say that 

 he obtained it from a whale. Indeed, he recognises its 

 essential distinctness from the original whale-louse de- 

 scribed bv Friderich Martens, but accuses Linna?us of 

 having considered them one and the same. Linna-His, in 

 his attempt to embrace the whole world of natural history, 

 no doubt committed many errors, but this particular one 

 was plainly out of his reach. The part of his tenth 

 edition, in which according to Baster he made it, was 

 published in 17.58, while the Pycnogouida, as already 

 explauied, were not known before 1762. Still, as everyone 

 is aware, Linnaeus was a man of very obliging temper, 

 and accordingly in 1767 he actually did commit the fault 

 of which he was falsely accused in 176.j. In his twelfth 

 edition he makes Martens' whale-louse a synonym of 

 Briinnich's Pyrtiogonum under the title of PhalaiKjium 

 haUvnarum, and this specific title is retained even in 1794 

 by J. C. Fabricius, although it had no claim to supersede 

 Strom's earlier littorale, and although the Pycnogonida 

 have nothing to do with baleen whales or any others. 



Ci/am 



>■ ceti (Linn.). After 

 F. Martens. 



Pycnogonum Hllorale (Strum). 

 After Briiunicli. 



there are four simi>le eyes ; in the former there are only 

 two, but Saviguy found in addition two compound eyes, 

 which no other naturalist has seen before or since, and 

 strangely enough the critics appointed to report on his 

 essay, though evidently not at all disinclined to find 

 faults in it, credit him with this imaginary discovery as 

 something of considerable importance. For some reason 

 he does not lay any special stress upon it himself. To 

 compensate for this self -denial he makes the extraordinary 

 observation that " Crustacea have not, properl}- speaking, 

 any abdomen, and the Pycnogonid group are distinguished 

 from other Arachnids by the length of their thorax and 

 the extreme smallncss of their abdomen." It is true that 

 the Caprellidea have the abdomen singularly reduced, but 

 in this respect they are exceptional not only among the 

 Amphipoda but among all Malacostraca, and not only 

 among them but among all free-moving crustaceans. To 

 say that a lobster, for example, has no abdomen, so far 

 from speaking properly, would be to make a statement as 

 absurd as could well be devised. Savigny, however, was 

 chiefly concerned to establish a parallel between the 

 appendages of the trunk or thorax in the two animals 

 under comparison. In an auiphipod or isopod, the 

 cephalic division or "head" carries six pairs of appen- 

 dages. Then comes the trunk with seven pairs, which 

 are all faithfullv represented in Gyamus, though in a 

 dorsal view the first pair are not seen, being concealed 

 under the second, and, as previously mentioned, the third 

 and fourth pairs are imperfectly developed. With this 



In whatever mistakes it may have originated, the 

 coupling together of Cyamus and Pycnogonum made a 

 comparison between the two a task as it were marked out 

 and prepared for Savigny's hand. In the latter genus 



Cyamus cell (hinu.). Magnified. Aftw' Lutlieii. 



state of things Savigny compared a species of NympJioii, 

 in which he maintained that the cephalic part, or head, 

 was constituted only by the proboscis, devoid of any 

 distinct appendages, and that the seven pairs attached 

 behind the proboscis answered to the seven pairs of limbs 

 in the trunk of an amphipod. That in some of the 

 Pycnogonida the first, the second, and in one sex the 

 third, of the seven pairs may be wanting, is no impedi- 

 ment to Savigny's hypothesis, since in Cyamus also, two 

 of the pairs have suffered degradation, and in both the 

 compared groujts abdominal limbs are, as a rule, con- 

 spicuous by their absence. But since the mainstay of 

 Savigny's comparison is the numerical fact, that in each 

 case the middle-body of the animal normally carries 

 seven pairs of appendages, it becomes apparent that the 

 comparison is definitely tied to the Malacostraca, among 

 which alone that numerical arrangement is found. In 



