149 



have become too greatly modified along their own lines 

 of specialization in regard to those particular structures 

 most frequently used in comparative morphology to be 

 of much value for a phylogenetic study of the develop- 

 ment of the different parts of the body in the lower 

 arthropods. Among the "Annelida," on the other hand, 

 we find some very ])r()itiisiim' inalcrial for sucli a study, 

 especially among tlio (•!ia't()i)u(la!i aiiiii'lids. >ucii a> the 

 Syllidai (e. g., Dujanlmni mhh eic). wliirh have seg- 

 mented appendages, while others of the grouj) liave de- 

 veloped structures no k'ss interesting from the stand- 

 point of pliylogeny, indicating tliat they have departed 

 but little from the ancestral condition of the arthropods. 

 The segmentation of tlie body of these annelids,'* tlie 

 nature and relative i)ositions of tlie lieart and the di- 

 gestive, nervous and other systems, very readily lend 

 tliemselves to such an interpretation, and it is not a ditlfi- 

 cult matter to derivi^ the head reuioii of a pi-iinitive 

 arthropod from that of the atincli<l type ( r>ci'iia rd, 1^!>-!), 

 or to derive the ai)]>('ii(la,ues of such au a ft h lopo*! tVoiu 

 those of the annelidan tyi)e, as has hfcii rc-.Miily dis- 

 cussed by Borradale, 11)17. 



In connection with the discussion of the (h ri\Mtinii of 

 the appendages of the lower artliro))od> from >tnirtures 

 co7np;ifa!)h' to the i)ara])odia of the annelid^, it mav he 

 retnarkod that the attempt of I^aiikoM.T. \^rl. to dctiNe 

 tho Ai1hi-op.)da Ml. .IV dirertly fmm tlio K'otifora. >u.-li 

 a^ the ivmai-kahh. ]^r,!ahnn nnm (NNlm^e ap|Mmdaire- 

 and the -'anu^" of the male A^i>hi,>h,n, he e.,mpare>; 

 to Ihr moNahle .pine, of T,n,,ilna and PnhnnHn.,). has 

 not IxH'u i)roduetive of as impoi-taut i-esults a> tlio-e ob- 

 tained from the comparison of the annelidan >tniclnres 

 with those of the arthropods. This, however. i> merely 

 to be expected, since the annelids lia\e dexclepet] far 



