74 S- (jOTO. 



descril)ed l)y Pintner, Avhicli is situated outside the cuticulnr meiu- 

 brnne. l>ut to me it seems that tlie mere presence of a cuticle is 

 mor{)lioh)gic:d]3Mi (|uite unimportant matter, so that the " Aussen- 

 epithel " of Pintner is as trnJy an epithelium as that of the ex- 

 cretory canals of the Nemertinei, just as the cells that produce the 

 chitinous wall of the trachea of insects are as truly of an epithelial 

 natin"e as any others that do not secrete chitin. Then as to the dif- 

 ference of the terminal " Kolben " of the Xemertinei from the 

 terminal excretory cells of other flat-worms, it seems to me that this 

 is also of (juite a secondary significance ; tliat an org'îin consists of a 

 single cell does not attbrd, it seems to me, any more reason against its 

 homology with a multicellular organ than the fact that an organ 

 consists of five cells is any ü'round ar^ainst its being homologous with 

 another consisting of six cells. If, on the other hand, we do not take 

 into account the number of cells, there is a striking similarity between 

 the terminal excretory organs of the Xemertinei and «jther PlatViel- 

 minthes. I therefore l)elie\e that the excretory systems of the 

 Plathelminthes, the Xemertinei inclusive, have all been derived fi-om 

 the same j)rimitive form, in other wf)rds, that they are homophyl(Mis. 

 To recapitulate the ab(^ve discussion, it is my opinion thtit the 

 term 'intracellular" is (|uite inapja'opriate to the excretor}' system 

 of the Trematodes and the Turbellaria, as it gives occasion to much 

 misapprehension and prevents the true understanding of the exact 

 state of the matter. It is also my opinion that the excretory systems 

 of the Xemertinei and the other Plathelminthes are phylogenetically 

 of the same origin, tlie number of cells that compose the various 

 parts of the system l)eing of cpiite secondary importance in discussing 

 its phylogeny.'^ 



1). Whituian, from a totally different point of view, comes to the same conclusion. He says, 

 " The nephrostome is a nephrostome all the same whether it consists of one cell, two cells, 



