KONGL. SV. VET. AKADEMIENS HANDL. BAND. 21. N:0 9. ' 29 



Ray Lankester raentions a movable part in the coxa3 of the third pair of appen- 

 clages (first pair of walking limbs) of the scorpions, corresponding to the epicoxite of 

 the coxa3 of the same pair in Limulus; but we have not been able to find this part 

 in the scorpions exarnined by us. 



The shape of the loalking limbs in Palseophonus, especially of their terminal joint, 

 which might seem to indicate a closer relationship between this scorpion and the Eu- 

 rypterids, is,, as we have already remarked^), also met with in several other, widely 

 different Ai^thropods, and consequently cannot be adduced as evidence for an affinity 

 between the groups in question. 



The comparison between the compound ei/es of the Merostoms and the few sim- 

 ple lateral eyes of the scorpions, is scarcely tenable. The Merostoms, and their close 

 allies the Trilobites, show, as regards their eyes, a striking resemblance to Äjms and 

 especially to Arguliis; and we think that one of the chief arguments for a coniraon 

 origin of the Merostoms and the Trilobites on the one hand, and of the Phyllopods, 

 Copepods and other Entoinostraca on the other, is to be found in the arrangement 

 and structure of the eyes. — The base of all the ambulatory appendages of Apus forms 

 a process which serves as a jaw-organ, just as in the Merostoms; in Apus and other 

 Phyllopoda, just as in Limulus, the two anterior pairs of appendages (the «antenna3») 

 receive their nerves from the oesophageal collar, not from the cerebral ganglion, thus 

 contrary to what is the case in the scorpions. 



It may here be remarked that the median lamella which in the Copepods unites 

 the bases of each pair of natatory limbs, is not, as stated by Ray Lankester, formed 

 by the coalescence of the bases of the legs themselves, but is a separate median pro- 

 cess, just as in Limulus. 



Michael's discovery^) of super-coxal glands in some of the Acari (Oribatoidte), 

 which he, probably rightly, compares with the segmental organs or nephridia of the 

 Worms and the coxal glands of Limulus and the Scorpions, seeras to confirm Bert- 

 KAu's^) opinion that these organs, Avhich occnr in many Crustacea and Arachnida, are 

 inherited fi^om common, low-standing ancestors, and that their presence in Limulus 

 and the Scorpions is thus no evidence of a closer relationship between these animals. 



Among the other characters, on the strength of which the Merostoms — or at 

 least Limulus — have been considered as nearly related to the scorpions (compare Ray 

 Lankester, 1. c, p. 66 and 67), some are also met with in several undoubted Crustacea, 

 as Ray Lankester himself admits. Of the remaining characters common to the groups 

 before us, Udo only would seem to be of special importance, viz., the presence of a 

 fibro-cartilaginous entosternite in the cephalothorax, and a certain agreeraent in the struc- 

 ture of the organs of generation, shown especially in the genital apertures being situ- 

 ated under an y>operGiduiiv> on the iirst segment of the abdomen. But these characters 



') See above, p. 18. 



-) A. D. MiCHAEL, Observations on the Anatomy of the Ovibatidte, in Journ. of the Roy. Microscop. Soc., 



Ser. 2, III, p. 21. 

 ■*) Ph. Beetkau, Ueber den Verdammo-sapparat der Spinnen, in Archiv f. Mikroskop. Anatomie, XXIV (1885), 



p. 447. 



