38 



KNOWLEDGE 



[Fmiruarv, 1902. 



It would be absurd to say tliat thoso aniiuiils are 

 popularly knowu as sea-spiders, since there is really no 

 ]Mipiilur "knowledf^e conieruius? tln-ni. Vernaeular names of 



Nt/mji/ion ma 



■■ (Strom). Natural i 

 After E. B. Wilson 



this kiud obtain a certain currency, because in regard 

 to things strange and unaccustomed we are always longing 

 to be able to speak and to hear every man in the tongue 

 wherein we were born. But in the expression " sea- 

 spiders " there is the special disadvantage that it prejudges 

 a case which is still being argued. Though they are 

 certainly not spiders, the question remains open whether 

 their relationship to spiders is too remote to admit of 

 their bemg grouped anywhere near them, or along with 

 them at all, in the Arachnida. Their scientiiic name is 

 properly derived from the earliest genus established in 

 the group, P(/c»0(/oh itm, Briinnich, 1764, and simply refers 

 to a striking external characteristic, the " frequent angles" 

 which their structure in general, and their limbs in 

 particular, display. The Arthropoda, that vast division 

 of the animal kingdom, which includes our present group 

 along wth Crustacea, Arachnida, Myriopoda, and the 

 uncounted legions of the Insecta, are named from the 

 common character of " jointed legs." In the Pycnogonida 

 more uuifoi-mly than anywhere else is the sigiiificauce of 

 this name " arthropod " justitied. For here the legs are 

 the predommant structures in the organism, and their 

 geniculations are as obtrusive and pertinacious as in any 

 harlequinade. So decided is the prominence of the legs 

 that in the early part of the nineteenth century Dr. Leach 

 named the tribe Podosomata, meaning leg-bodied animals, 

 and in the later part of the same century Gerstaecker and 

 Dr. Anton Dohrn adopted for them the name Pantopoda, 

 meaning animals that are all legs or nothing but legs. 

 These designations, therefore, come to much tlie same 

 thing as saying in English that the animals have no bodies. 



* This species is eommouly called Ntfrnplion strbmii, KrSyer ; it 

 identification with Strom's species being more or less conjectural. 



That, however, is by no means literally true, and accor- 

 dingly there is no scientific warrant for displacing the 

 earlier name Pycnogonida iutroduccil liy Latreille. 



Dr. Dohrn in 18(j9, fresh from studyiii'^' the group at 

 Millport, in the island of Cumbrae, de<larcd that, speaking 

 generally, all English zoologists at that time considered 

 it to be of crustacean nature, and that with equal unani- 

 mitv all German zoologists referred it to the spiders. As 

 a matter of history, then, it is worth while recalling that 

 in the first volume of our English Zoological Reconl, which 

 is the volume for 1864, Mr. Speuce Bate writes of the 

 " Pycnogonidae " as follows : " In adding this family to those 

 of Crustacea, we do not consider that we are pledging 

 ourselves beyond identifying it as a link that connects the 

 Crustacea with the Arachnida. Although the result of 

 recent research, both in the structure and development 

 of these animals, tends to place them among the Arach- 

 nida, there are some points in their structure that asso- 

 ciate them with the Crustacea ; this, together with old 

 association, induces us to speak of them in this place for 

 the present." This old association may refer to the work 

 of Johnston in 1837, and of Goodsir five or six years later, 

 but Ijeach in 1815, in a famous contribution to the 

 Transactions of the Linuean Society, most expressly in- 

 cludes the present tribe in the Arachnida, and Adam 

 White, in 18-57, excludes it from his "History of 

 British Crustacea." Moreover, in the volumes of the 

 Zoological Record the esteemed German writei". Dr. von 

 Martens, who succeeded Spence Bate as recorder of crus- 

 taceans, followed his example down to the year 1874. 

 There is, therefore, no such Anglo-Teutonic cleavage of 

 opinion as Dr. Dohrn supposed. Much rather are two 

 illustrious French authors mainly responsible for up- 

 holding the crustacean aftiuities of these spindle-shanks. 

 For a long time the " Histoire Naturelle des Crustaccs," 

 by Henri Milne-Edwards, deservedly held the field as the 

 only moderately complete, comprehensive, and trustworthy 

 history of that class. Daring its reign there would have 

 been few desirous, and still fewer effectively capable, of 

 disjjuting the historian's opinion on an obscure issue 

 which is thus expressed in his third volume (1840) : — 

 " It is only with much hesitation that I place here a little 

 group of articulated animals which have been considered 

 by most zoologists as belonging to the class of Arachnida, 

 but which seem to me to have more analogy with the 

 Crustacea, for they have no tracheae nor lung-books for 

 atmospheric respiration, and they do not appear to breathe 

 the oxygen dissolved in water except through the general 

 surface of the skiu, as we have seen to be the case iu 

 several lower crustaceans." Much earlier, in 1816, Jules 

 Cesar Savigny, in his striking essays on Invertebrata, 

 stoutly argued that, if the group were not actually crus- 

 tacean, it was the link which most certainly connected 

 that class with the arachnids. In those essays Savigny 

 had at least one memorable success, namely, that which 

 attended his homologizing, as it is called, the limbs of the 

 Malacostraca. He demonstrated that the very organs, 

 which in one set of them are parts of the mouth-apparatus 

 and concerned with feeding, or, in one word, are jaws, in 

 another set are prehensile or ambulatory limbs, answering 

 to the description not of jaws but of arms or legs. One 

 need not perhaps be surprised that he attempted to extend 

 this discovery in other directions, and hoped to find in it 

 a key for solving fresh problems. 



Savigny was very well aware that in the Pycnogonida, 

 when they are most fully furnished with appendages, there 

 are never present more than seven pairs, whereas in the 

 Malacostraca when fully furnished these pairs amount to 

 nineteen, without counting the stalked eyes. This being 

 so, he was under much of an obligation to compare a 



