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The lateral praeoral cavilies are derived trom the collar-cavities, and are in fact the 

 antero-dorsa! iirocesses shewn in Hatschek's wcll known hgs. 50 — 52 (81) of an embryo of 

 Amphioxus. The remainder of the collar-cavities is constituted by the right and left stomocoels, 

 together with at least ihree myotomes (p. 68), and the anterior parts of the metapleural canals. 

 These had been supposed by MacBridl;, in his earlier paper (98), to belong entirely to the 

 collar, but van W'ijiie considers that their innervation shews that they belong for the most 

 part to the metasome, only their antericjr ends belonging to the collar. The collar thus ends, 

 as in Enteropneusta, at the beginning of the branchial region, and the more posteriorly situated 

 coelomic spaces belong to the metasome, which by a secondary segmentation has given rise 

 to the remainder of the myotomes. The collar-canals oi the Hemichordata are represented in 

 Amphioxns by the first pair of nephridial tubules, which open from the epipterygial cavities 

 (-— parts of the collar-cavities) into the atrium. 



Van Wijhe thus definitely recognises the affinity of the Hemichordata to Amphioxus. 

 The latter is indeed placed, with the Tunicata and the Craniata ("Craniota") in the Chordata; 

 while the Enteropneusta and Ceplialodiscus^ constituting the Pharyngotremata, are associated, 

 with Rhabdopleura and Plioroiüs (to which no group-name is assigned) as Prochordata. But 

 he carries the comparison even further than has been done b)- most morphologists, since he 

 considers (p. 69) that the protocoel, mesocoels and metacoels can be identified in the embryos 

 of Pefroii/yzoit, Elasmobranchs and even in the higher Craniata, while (p. 70 n.) a proboscis- 

 pore can be recogni.sed in the embryos of Elasmobranchs. 



It appears to me that a critical examination of van Wijhe's views can only be made 

 as the result of an independent investigation of Amphioxus; but there are nevertheless one or 

 two points on which I should like to comment. The account of the collar-cavities is undoubtedly 

 of interest, confirming as it does the general accuracy of MacBride's observations on the 

 develo})ment of Amphioxus. Fig. 27, 28, and 32, given by van Wijhe, are specially significant 

 in shewing the existence, in the adult Amphioxus, of a well marked transverse septum between 

 the collar-cavities and those of the metasome. The prolongation of the outer lip-cavity into the 

 oral cirri may indicate that the floor of the buccal cavity corresponds with part of the operculum 

 in Ccphalodisc2is, while somewhat further back the collar-cavit)- is subdivided by a ventral 

 mesentery (cf. figs. 9 — 18), as in the same animal. The backward extension of this region of 

 the collar, on the ventral side of the pharynx, is also suggestive. Thus van Wijhe's fig. 15 

 represents an arrangement which is similar to what may be seen in sections of Cephalodiscus 

 transverse to the long axis of the zooid, in which the metasomatic cavities occupy the dorsal 

 part of the section, while the collar-cavities still appear on the ventral side, subdivided by a 

 median mesentery. Taking this into consideration with Hatschek's figs. 50 — 52 (81) of an embryo, 

 there is a remarkable similarity between the collar-cavities of Cephalodiscus and Amphioxus, 

 the coelomic sac in both cases having a triangular form when seen from the side, the dorsal 

 part being much longer than the ventral part. While in CcpJialodiscus the elongated dorsal 

 region of the collar-cavity is connected with the arms, the anterior parts of the same region in 

 Amphioxus are cut off to form the lateral praeoral cavities ("Schnauzenhöhlen") of van Wijhe. 

 The relations of the collar-cavities of the larval Amphioxus to the notochord and to the ventral 



