IV 



PEONEPHEOS 



227 



the splanchnocoele, the chamber containing the glomerulus appearing 

 to be a side branch (Fig. 124, C), or on the other hand the pro- 

 nephric chamber appears to form the dilated end of the tubule while 

 the peritoneal canal appears to form a side branch (Fig. 124, D). 



In connexion with what has been said it is important 'that the 

 student should get clear, in his mind from the beginning (1) that 

 the cavity into which the glomerulus projects (known as the cavity 

 of the Malpighian body in the more highly evolved types of kidney) 

 is simply a more or less completely separated off portion of the 



a.n.d. 



Fig. 124. — Illustrating variations in the relations of nephrocoele, tubule and peritoneal 

 canal in the pronephros of JTypogeophis. 



a.n.d, archinephric duct ; tic, nephrocoele ; ns, nephrostome ; p.f, peritoneal funnel ; t, tubule. 



coelome (nephrocoele) and that neither it nor the peritoneal canal is 

 to be regarded as a portion of the tubule, and (2) that the actual 

 tubule commences at the nephrostome or opening leading into it 

 from the nephrocoele. The word nephrostome throughout morpho- 

 logy means an opening leading from coelome into nephridium. It 

 is necessary to accentuate this because in many embryological 

 writings the term nephrostome, or nephrostomal canal, is applied to 

 the peritoneal canal which is not an opening leading from coelome 

 into nephridium but simply a communication between the splanch- 

 nocoelic and the nephrocoelic portions of the coelome. A clear 

 appreciation of these points is of help in facilitating the comprehen- 

 sion of a difficult chapter in Vertebrate morphology. 



