Classijication of the Arthropoda. 369 



pairs of antennge, the second of wliich represents the first 

 pair of trunk-members removed forwards. — Series II. (Gigan- 

 tostraca, Araclmoidea). Absence of the anterior antennae. — 

 Series III. (Onychophora, Myriapoda, Insecta). With au 

 rior pair of antennae, representing the frontal tentacles of the 

 Annelida." 



With the exception of the fact (to which I will return 

 below) that Professor Glaus regards only the second instead 

 of both pairs of Crustacean antennae as representing trunk- 

 members which have been removed forwards, this statement 

 is identical with that made by me as follows in '' Limulus an 

 Arachnid," and is contrary to the views advocated by Pro- 

 fessor Glaus prior to my publication. Speaking of the 

 probable ancestral history of the three great stems of Arthro- 

 poda recognized by me and now adopted without acknow- 

 ledgment by Professor Glaus, I say : — " In the interval 

 between the giving off of Peripatus and the production of the 

 Phyllopod-like ancestors of the Crustacea from the aquatic 

 Pro-Arthropoda a vast change had to be effected in regard to 

 appendages, as well as in the fusing of the nerve-cords, abo- 

 lition of nephridia, production of a compound eye, striation of 

 muscular tissue, &c. The 2^^'ostomial antennce disappeared, 

 and their place was taken first by one, then by two pairs of 

 postoral appendages, wliich gradually acquired a pra^oral 

 position, as actually occurs in their individual growth in the 

 embryo at the present day. . . . The otlier appendages pro- 

 bably all acquired at one stage a development of their basal 

 portion, which served as an accessory organ for the purpose 

 of bringing food to the mouth and, in some degree, in crushing ' 

 such food (as seen in Apus). . . . The definite Crustacean 

 character was attained when two pairs of appendages had 

 become prseoral and at least three pairs specialized as jaws 

 and no longer locomotor. . . . Probably none of the known 

 Merostomata suffice to give us a true picture of the structure 

 of the ancestral Merostomata from which they were all 

 derived. Probably these ancestral Merostomata were devoid 

 of the prostomial antennce — the non-appendicular antennge. 

 At the same time none of their postoral appendages had 

 become definitely prasoral in position and nerve-supply, 

 though not less and probably not more than six pairs of 

 pediform appendages were closely set round the mouth, their 

 bases acting as powerful manducatory organs." 



I then proceed to state the probable mode of the derivation 

 of the Xiphosura, the Eurypterina, and the living Araclinlda 

 from these primitive Arachnids, destitute both of the prosto- 

 mial antennge characterizing Peripatus and its descendants, 



