1 2 I 



the arms aiul the mantle beloiiL;- to ihc collar. Xow those zoologists who have supported the 

 \'ie\v that the Brachiopoda are related to PJioronis and to other tentacidiferous animals have 

 assumed that tlie lophophores are hcjiiiologous structures in the several groups. If then the arms 

 are to be regarded as the representatives of those of PhoroJiis or Cephalodiscus^ it seems to 

 follow from the evidence of Lingula that the mantle-fold is not part of the collar; — or, in 

 other words, that the structure which in the larvae of certain Brachiopods appears to represent 

 the collar is not in realit\- of that natnre. I do not in fact find much in Yatsu's account which 

 obviously confirms the view that the Brachiopoda are related to the Hemichordata. 



It must, however, be noted that Blochmann '), as the result of his careful studies on 

 the anatomy ot Brachiopoda, is convinced of the affinity of this group to Plioronis, the Sipun- 

 culids and the Polyzoa. The relationship is nearest between Brachiopods and PJioronis^ with 

 which the Sipunculids are connected ; while the affinities to the Polyzoa are more remote. 



I do not feel myself qualified to criticize the view of the Brachiopod affinities of the 

 Hemichordata, particularly in the absence of Information with regard to many features of 

 importance in the later development of the Brachiopoda. But the testimony of such authorities 

 as Blochmaxn cannot be ignored; and if this observer is right in maintaining that the 

 Brachiopoda are related to Phorojiis, it may perhaps follow that they are also related to 

 Cep/ia lodisciis . 



Although it appears to me probable that the Hemichordata are related both to the 

 Echinodermata and to the Chordata, I do not propose to discuss these questions at length, 

 since their consideration is more easily approached from the side of Balanoglossus than from 

 that of Cephalodisciis. Independently of the papers dealing with the resemblances of Tornaria 

 to Echinoderm larvae, the affinity between the Enteropneusta and the Echinodermata has been 

 maintained by Bury (88, p. 295; 95, p. 125), MacBride (96, p. 395), Masterman (98, i, p. 289; 

 02, p. 403) and others, and it is recognised as possible by Spengel (93, p. 750). 



The question (jf the Chordate affinities of the Hemichordata has formed the subject of 

 numerous papers. As long ago as 1877 Huxlev (77, p. 674) went so far as to institute a group 

 Pharyngopneusta for the reception of the Enteropneusta -|- Tunicata, in allusion to the existence 

 of gill-slits in both groups. The affinity is rejected by Spexgel (93, p. 721), but it is supported 

 by Batesox (86), Mastermax, MacBride (98, 00), Wiixev (94; 99, 2, p. 295) and others. 

 Kemna (04, pp. so, 52) considers that CepJialodisciis more nearly resembles the common ancestor 

 of the Chordata than does any other living form. Although I do not discuss the views of these 

 writers, the important recent work by vax Wijhe (01) on the head of Amphioxus seems to 

 me to call for special remark. 



Van Withe accepts, though with some modifications, MacBrides account (98, 00) of the 

 development of the coelomic cavities of Amphioxus, according to which the embryo is constructed 

 on the Hemichordate type so far as it po.ssesses representatives of the protocoel, the mesocoels 

 and the metacoels. 



I) F. Blochm.'^xx. "Über die .Anatomie und die vevwandtschaftlichen Bezieliungen der Brachiopoden", .\rch. d. Ver. d. 



Kreunde d. Xatg. Mecklenburg. Jg. 46. 1892. p. 37. 



SIBOG.^-EXPEDITIF. XXVI tó. 16 



