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. 



Group 



Abchimeeic^ System 



Essential Organs 

 or Excretion 



Ideal 



Protomeric pores 



Mesomeric pores 



Opisthomeric 

 pores 



Regional pore-canals 



Enteropneusta 



Proboscis pores 



Collar pores 



Truncal pores 



{Spengelia) 



Glomerulus 



Cephalochorda 



Praeoral pit + 

 olfactory pit 



Hatschek's 

 nephridium 



Lankester's 

 brown funnels 



Boveri's nephric 

 tubules 



Urochorda 



Neuro-hypophysis 

 (in part'*) 







( Renal vesicles ; 

 j Organ of Bojanus 

 ( (Molgulidae) 



Vertebrata^ 



Hypophysis 

 cerebri (in part^) 







( Pronephros 

 ■j Mcsonephros 

 ' Metanephros 



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. 



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

 aflirmed 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. 



^ In part because eoelomic element is wanting. 



