June, 1902.] 



KNOWLEDGE 



139 



always present, always tliree-joiuted, always chelate. By 

 that fact may be justified the convenient designation 

 " chelifori," which has bt^eu applied to them, since in all 

 specicB they are at least for some part of the animal's 

 life carriers of chelae. Still such a title is merely 

 neutral. It is .secure from criticism because it leaves 

 out of sight considerations of homology. It is un- 

 helpful to those who would fain know the relation of 

 these chelifori to corresponding appendages in other 

 arthropods. In this respect there is an embarrassing 

 choice of opinitm, for some think them equivalent to the 

 first pair of antennip and some to the second, some to the 

 mandibles, and some to a pair of maxillipeds. It is, 

 perhaps, worth while going a little out of our way to 

 illustrate the perplexing obscurity of the problem. A 

 remarkable arachnid, Kienenia mirnij'/i.s-, first described by 

 the Italian authors Grassi and Calaudruecio, was after- 

 wards more exactly studied by the Danish savants H. J. 

 Hansen and W. Sorensen. Eecently Dr. Meinert, while 



Kanenia mirabilis, G. and C. Aftt'r Hansen. 



referring with high praise to the description and figures 

 supplied by his colleagues at Copenhagen, deduces from 

 them a conclusion which they themselves do not accept. 

 He finds in Kienenia a proboscis homologous with that of 

 the Pycnogonida. Projecting in front of its mouth are 

 seen a pair of " antennae," thi-ee- jointed, chelate, which 

 not a little resemble the pycnogonid first appendages. 

 There is a further point of comparison. In the scorpions, 

 pseudoscorpions, and many of the Pedipalpi, the 

 "cheliceroe" are followed by long chelate organs forming 

 the second pair of appendages. In the Pycnogonida the 

 second pair, though as variable as the first, are never 

 chelate, and in this respect they again agree with 

 Kwnenia as well as with some of the Pedipalpi. But 

 Kienenia, it will be seen, has only six pairs of aj^pendages, 

 not the mystic pycnogonid seven. Among all the 

 peculiarities of the latter group it would surely not be the 

 least, if Kienenia with the abdomen abnormally developed 

 could be proved to be the nearest living relative of a tribe 

 which has the abdomen abnormally insignificant. Such a 

 conclusion is at present highly improbable. 



The second appendages, or "palps" as they have been 

 most commonly called, have a number of joints varying 

 from ten to five, and are liable to vanish entirely. When 

 present they have their place of attachment generally 

 close to the chelifori, and a neck-like constriction of the 

 supporting segment often puts them far apart from the 

 ovigerous legs. Yet, when the segment is very short, 

 they are sometimes brought into dose contiguity with 

 these, which in their turn lie close to, or rarelv at a little 

 distance ajiart from, the first pair of walking-legs. The 

 ovigerous function has been already discussed. The third 

 appendages to which it belongs have other claims to 

 attention. In the first place, however convenient they may 

 be to their possessors, they are very trying to the syste- 

 matist. Tliey helped Savigny to a comparison of the 

 Pycnogonida with a crustacean type, but it was fanciful 

 and untenable. When the comparison is transferred to 

 all existing Arachnida, Kienenia mirabilis included, this 

 third pair of appendages appears to be a pair too many. 

 Semper overcomes this difficulty by regarding them as a 

 new formation, and Meinert thinks this a fair solution, in 

 opposition to Dohrn, who regards it as an explanation 

 which merely confesses inability to explain. In regard to 

 the Entomostraca a theory was long maintained by the 

 late distinguished professor, Carl Claus, that the two 

 branches of a crustacean hmb could separate and form 

 two apparently distinct appendages. He sometimes com- 

 plained that this discovery was ignored or not sufficiently 

 appreciated by the scientific world. One sees how exceed- 

 ingly convenient it would be in the present difficulty if one 

 might suppose that the second appendages in the Pycnogo- 

 nida were mere offsets either of the first pair or the third. 

 There are obstacles in the way of this solution. The 

 bifid structure, so common in crustacean appendages, has 



Ovigerous leg of Colossendeis gigas, Hoek. 

 Hoek. 



Xatiiral size. Prom 



no pi'ominence in those of the Arachnida or Pycnogonida. 

 But the position of affairs would not be much improved if 

 it had, for it so happened that, just as the world was 

 coming to accept the late professor's theory, solid objections 

 were raised to it by other naturalists and eventually it was 

 abandoned by its author. The origin, then, of this third 



