368 Prof. E. Ray Lankester 07i the 



prostoinlal tentacles of Chcetopod worms, and not (as I sug- 

 gested, in 1873, are the antenna? of the Crustacea) truly 

 postoral appendages which liave acquired a secondary pra^oral 

 character by the backward shifting of the oral aperture. This 

 view as to the Cheetopod affinities of the antennas of Perijxitus 

 and Insecta, and as to the contrasted and totally distinct origin 

 of the Crustacean antennae, is adopted from my writings by 

 Prof. Claus. My words in " Limulus an Arachnid " are : 

 " The antennaj of Hexapods and of Myriapods may be, as pro- 

 bably are those of Peripatus, non-appendicular prostomial an- 

 tennse." And again, ''The anteunte of Peripatus probably 

 are identical with the similar organs of Chfetopoda, and are 

 not originally postoral appendages." Further, in the memoir on 

 the " Appendages and Nervous System of Apus," published 

 in the Quart. Journ. Micr. Sci. in 1881, I say (p. 368) : — 



" I have long been of the opinion which Professor Claus 

 appears to hold, that the appendages of the Arthropoda are 

 homologous (oi-, to use a more distinctive term, ' homo- 

 geneous ') with the appendages of the Chsetopoda; and on 

 this account I consider it a proper step in classification to 

 associate the Chaitopoda with the Arthropoda and Rotifera in 

 one large phylum, the Appendiculata (see '' Notes on Embry- 

 ology and Classification," Quart. Journ. Micr. Sci. 1876, and 

 Preface to the English translation of Gegeubaur's ' Elements 

 of Comparative Anatomy '). 



" At the same time I have not been led to conclude, as 

 does Prof. Claus, that only one pair of the Crustacean 

 antennas are to be regarded as primarily postoral in position 

 and as representing the appendages of an originally post- 

 oral somite * ; but I think it probable that both antennae are 

 in this case, and that in the Crustacea there is no represen- 

 tative of the antennae or tactile processes of the cephalic lobe 

 of Chastopoda. Whilst this appears to me probable in regard 

 to the Crustacea, it yet seems to me very possible that the 

 antennas of Peripatus and of Hexapod and Myriapod insects 

 may represent true processes of the cephalic lobe or prosto- 

 mium, as seen in Chastopoda." 



I have independent reason for concluding that Professor 

 Claus has read the passage just quoted. He makes use of it 

 in giving the characters of the three stems of Arthropoda, 

 which he now adopts in accordance with my views as follows, 

 so far as the question of antennas is concerned. 



He gives as characters: — "Series I. (Crustacea). Two 



* By an error of the press the original here quoted reads " two origi- 

 nally postoral somites." — E. R. L. 



