424 EDWIN S. GOODlilCH. 



the highly modified Chgetopods^ which are supposed to be 

 derived from them, in the Bay of Naples ? The absence of 

 parapodia aud of cha^tte are the only characters which seri- 

 ously entitle the Polygordiidee to such a bold claim. There- 

 fore, if it can be shown that both chsetse and parapodia have 

 been reduced or even lost in other cases; and if, further, it 

 can be shown that the Polygordiidae are quite nearly related 

 to a form possessing pai-apodia and chaetee, the '' Archi-annelid 

 theory " will be severely shaken. 



That parapodia may disappear more or less completely is 

 shown in many families of Polychtetes. One may mention 

 especially the Scalibregmidae, ChlorhaBmidae, Steruaspidse, and 

 the Opheliidge, to which family Mcintosh (9) and Giard (4) 

 believe Polygordius to be closely related. The Oligocheeta 

 exhibit an example of the total loss of chaetse (Anachgeta 

 and the Discodrilidee ?), and of course in almost all the Hiru- 

 dinea they have entirely vanished ; but amongst the Poly- 

 chaeta it may be pointed out that in Arenicola a considerable 

 region of the body is devoid of both chaetas and parapodia. 

 In Tomopteris also no ch?etae are present on the trunk seg- 

 ments. 



More important still is the near relationship which un- 

 doubtedly exists between the Polygordiidas and Saccocirrus. 

 Already Marion and Bobretzky, as mentioned above, remarked 

 on this affinity, and Fraipont has further insisted on it. But 

 the most convincing evidence seems to have been brought 

 forward by Langerhans (8) ; curiously enough it appears to 

 have escaped the notice of later writers on this subject. The 

 piece of evidence to which I refer concerns the very remark- 

 able contractile head cavity of Saccocirrus, hitherto generally 

 supposed to be unique. 



Describing Protodrilus (Polygordius) Schneideri, 

 Langerhans says, "Inneu von den Gefassen liegt, gauz wie 

 bei Saccocirrus, in den Tentakeln ein grosserer Hohlraum 

 (Fig. 47), welcher im Kopf zwischen Quergefass und Hirn 

 mit dem der anderen Seite zusammeuhangt, vou diessem 

 Verbiudungstuck geht ein kleiner dorsaler Forsatz ab 



