394 MR. H. M. BERNARD ON THE 



with other Arachnids sliows that these processes on the coxae, and even the position of the coxas themselves^ 

 are secondary specializations {cf. e.g. Thehjphonus). Further, these coxae were never jaws, inasmuch as 

 they do not work in the mouth, but behind it and below it ; the small pointed labium is quite a distinct 

 structure anterior to these so-called jaws. If the small labium could be found below them or wedged in 

 between them, so that they formed any part of the real boundary of the oral aperture, they might 

 perhaps claim to have once been jaws. But, in all Arachnids, the oral aperture is distinct and without 

 jaws. The nearest approach to anything like a pair of jaws working at the sides of the mouth is found 

 in the Spiders, where the coxse of the pedipalps form a hairy barrier on each side of the oral slit to 

 prevent the escape of juices, functioning in this respect like the coxa; of the pedipalps iu Thtlyphonus and 

 Phry-ims. 



If Limulus or Eurypterus was anything like the ancestral form of the Arachnids, how is it that all 

 traces of such specialized jaws as they possessed should have disappcai'ed ? In some important Arachnid 

 familv traces of true jaws would certainly have been found, had they ever existed in the ancestral 

 form. Instead of which we find a regular series of coxae showing a variety of specializations, which 

 only admits of being deduced from a series of uniform unspecialized coxal joints, certainly not from a 

 series of specialized jaws, 



14. The Coxal Joints. — The primitive form possessed a series of vxniformly developed 

 coxal joints, which vi^ere originally no doubt movable. The Spiders and Phrytms have 

 alone retained this condition. In all other Arachnids we find fixation of some or all 

 of the coxse, and great variations in their sizes and in their approximation towards the 

 middle line [cf. above paragraph on the sternites and PL XXVII. figs. 15-18, 

 PI. XXVIII. figs. 1-2). 



As stated in the last paragraph, I hold it impossible that all these varied developments of coxse could 

 be derived from a series of closely-compressed lamellate jaws working round a ventral mouth. If such 

 jaws could open wide enough to become useless in feeding, and thus to atrophy, allowing the mouth to 

 travel forward between them for an entirely different method of feeding (the sternites reappearing in 

 its wake!), we should expect to find, in some Arachnid or other, traces of the former biting-ridges or 

 teeth along the coxae ; we should hardly expect to find the large, round, smooth coxae looking so exactly 

 like the derivatives of a primitive undiflercntiated series. We should hardly expect either that these 

 gaping and atrophying jaws, which would become rigid during this useless time, would once more 

 become movable, once more approach the middle line, obliterating the sternites a second time, and then 

 again become fixed. And yet this must have happened if Limulus is to be genetically related with 

 Galeodes or Thelyphomts as a more primitive form. I repeat that I do not believe it possible for 

 specialized forms, in becoming adapted to a new manner of life, completely to lose all traces of their 

 former specialization. 



15. Vestigial Abdominal Limbs. — The primitive form, specialized, as Ave have seen, 

 into an anterior locomotory region and a posterior vegetative sac, retained for a longer 

 or shorter time the remains of the limbs on the latter region, which, owing to its 

 specialization, had become useless for locomotory purposes. Every segment had its 

 vestic:ial ambulatory limbs, which have now almost completely vanished, except when 

 retained for other functions. We have limbs modified into sexual organs, into sensory 

 feelers (pectines), into spinning-mamillae, and into genital or stigmatic opercula. Where 

 they have vanished as projecting limbs, they have simply flattened down, leaving in 



