314 



ENTEROPNEUSTA FROM THE SOUTH PACIFIC, 



accomplish this object on the assumption that the nephric tubules of Amphioxus (i.e. 

 as we know them in Amphioxus) represent the primordium of the Vertebrate kidney. 



1 In this table I have incorporated the terms archimeric, protomeric, &c. in the sense in which they 

 were introduced by Masterman ("On the Diplochorda, " Quart. Journ. Micro. Sci., Vol. 40, 1897, p. 281). He 

 describes the tripartite division of the coelom as archimeric segmentation, and the three archimeres are (1) Pro- 

 tomere, (2) Mesomere, (3) Metamere. The last is inadmissible because metamere already has a meaning of its 

 own, and I must therefore replace it, for my present purpose, by the term opisthomere. 



- In 1886 Bateson wrote : — " Upon the origin of the excretory system of Vertebrata nothing can be 

 affirmed from a study of Balanoglossus." I trust the above table will illustrate the progress that has been 

 made in this matter during the last ten or twelve years. 



3 In part because coelomic element is wanting. 



