August, 1902.] 



KNOWLEDGE, 



187 



its elevation above all other animals that, if a tribe were 

 discovered in whith each arm ended in a solid stump 

 instead of fingers, there would no doubt be little 

 temptation to consider it human. Yet, if it proved that 

 the infants had thumbs and fingers like our own, it might 

 be equally difficult to classify the offspring apai-t from 

 ourselves or the parents apart from their offspring. I'.ut 

 the young Ammothea is just in this position. To begin 



Ammothta magnirottris, Dohrn. <5. Only basal joints shoivn of 

 hinder legs. From Dohrn. 



with it possesses the grasping chelae stretched in front of 

 its mouth. Then, with advancing life it sacrifices this 

 advantage, first allowing the claws to occupy a seemingly 

 quite ineffective situation to the rear of the mouth, and 



Ammothea magnirostris, Dobrn. ilinute larva greatly 

 magnified. From Dohm. 



finally relinquishing their chelate character which in such 

 a situation had ceased to be of value. 



So fundamental is the importance of the chelate first 

 appendages in the opinion of Professor G. O. Sars, that 

 upon them he bases the primary division of the whole 

 group into three orders or sections. Leach in earlier days 

 on the same principle bisected it into the Gnathonia and 

 Agnathonia. Fuller knowledge now requires a tripartite 

 arrangement. Thus the Achelata are entirely without 

 " chelifori " except in the larval condition. The 

 Euchelata retain them throughout life. The Cryptochelata 



have them in the larval and young stages of their exis- 

 tence, but as adults lose them altogether or keep them 

 only in a rudimentary state. To the first section Sars 

 assigns two families, and three to each of the others. The 

 Achelata comjirisethe Pycnogonidas and the Chilophoxidse, 

 each with a single genus, and both agreeing in the absence 

 not only of the first appendages but also of the second, 

 the female sex wanting the third lilcewise. They differ 

 because Pycnogoimm, the representative of the first family, 

 stands almost alone in the restricted number of the 

 genital openings. Chilophoxiis, for which the second 

 family is instituted, has these apertures in all the 

 ambiilatory legs of the female and in the last three 

 pairs of the male.* Moreover, while Pycnogonum has a 

 certain portliness, which gives its typical species a claim 

 to be somebody among nobodies just as the one-eyed man 

 is a king among the blind, Chiloj^hoxus on the contrary 

 has nothing to show but attenuated personalities. The 

 typical species of this latter genus is among the earlier 

 known forms, having been described by Montagu in a 

 paper which was read at the Linnean Society in 1805 and 

 published in 1808. Montagu was under the impression, 

 shared as we know by many distinguished naturalists long 

 after him, that the ovigerous legs belonged to the female. 

 He correctly describes the position of the four eyes on their 

 conical tubercle, but adds that they " appear under a 

 microscope strongly reticulated." This would seem to 

 have been an ocular delusion on his part, for although the 

 modern method of section-cutting has revealed a reticular 

 tissue within the eye, such an observation would have been 

 unattainable by any implements at Colonel Mont;igu's 

 disposal. He also remarks that " on the back between 

 the hinder pair of legs is an erect cylindric tubercle, 

 which in some point of view might be mistaken for a tail." 

 Tail is an indefinite word or one might wonder where the 

 mistake comes in, for, if the part of the body which 

 follows the ambulatoi-y limbs may indifferently be spoken 

 of as the abdomen or tail in crustaceans, insects, and 

 scorpions, those expressions will be equally appropriate 

 for the cylindric tubercle of which Montagu is speaking. 



Not without some fear of evoking those electric flashes 

 that are ever ready to smite the rash disturbers of long 

 accepted terminology, I must here invite the special 

 attention of naturalists to the new names Chilophoxus 

 and Chilophoxidae, and to the cancelling of the names 

 Pallenidae and Pseudopallene in favour respectively of 

 PhoxichilidcB and Phoxichilus. This last-named genus 

 was instituted by Latreille in the " Nouveau Dictionnaire 

 d'Histoire Naturelle," torn. 24, p. 137, so far back as 1804, 

 not as has been stated in 1816. The only species assigned 

 to it was the Pycnogonum spinipes of O. Fabricius. It is 

 impossible therefore to retain Phoxichilus apart from that 

 species. Consequently Pseudopallene, Wilson, 1878, to 

 which both Sars and Meinert refer the above-named 

 P. spinipes of the " Fauna Groenlandica," becomes a 

 synonym of Latreille's far earlier genus, and the family 

 hitherto known as PallenidiB, from Palleae, Goodsir, 1837, 

 must be henceforward known as PhoxichUidae. All species 

 which have been assigned to Phoxichilus on the ground of 

 a real generic agreement with Montagu's Phalangium 

 spinosum must now be transferred along with this species 

 to Chilophoxus, while Pseudopallene circularis (Goodsir) 

 will find its place in the true Phoxichilus as now 

 reinstated. 



* Mr. Marshall's paper " On varialioQ in the number and arrange- 

 ment of the male genital apertures in the Norway Lobster" (Proc. 

 Zool. fioc. London, 1902), is worth considering in connection with our 

 subject, but with the crustiicein it is an increase in the number of 

 openings that is exceptional, whereas in the Pycnogonida it is the 

 diminution in their number that calls for remark. 



