385 



There is no communication, through the segmental organ, be- 

 tween the coelom and the exterior, — a very common disposition 

 amongst the vertebrates, for instance. 



Let us leave aside for the present the other details I have 

 pointed out. 



The reader has remarked that I do not speak in this description 

 of any recurrent part of the central tube or excretory canal. Is 

 it that I deny the existence of any such part? Not in the least. I 

 have on the [contrary expressly declared that this tube is very 

 sinuous — I have used the word "tortueux" that means ex- 

 tremely sinuous or winding. But I did not insist on the disposition 

 of these sinuosities because, as I have said, I have paid more 

 attention to the minute anatomy than to the external form that may 

 be easily studied by mounting the whole organ in balsam. I admit 

 the existence of all the circumvolutions Mr. Bourne may describe 

 with the aid of that kind of preparation, though I have abstained 

 from speaking about them, — exactly as any histologist would be 

 allowed to describe the digestive tube with appendages, salivary glands, 

 liver, etc., without speaking a word about the circumvolutions or the 

 recurrent disposition of the colon. 



The funnel question being put aside for the present, — with 

 also certain details of lesser importance, — I differ from Mr. Bourne 

 especially by the fact that I do not speak of any distinct and auto- 

 nomous mass of cells that would be run through, two or three different 

 times by a single tube. 



I have a very serious reason for doing so, and it is that I be- 

 lieve that no such masses exist on the nephridium. 



What Mr. Bourne designates as main lobe and apical 

 lobe are simply two parts of the tube with its sheath of cells, where 

 the sheaths of two parallel sections are put very closely together 

 and more or less united to one another (fig. 1, A — B). There is 

 nothing like a simple and homogeneous mass of cells pierced and run 

 through by two different sections of the same tube, one of them 

 deserving the name of recurrent duct; the sections are simply put 

 side by side. Their union is not so intimate that it might be taken 

 for a complete fusion. 



Mr. Bourne himself has observed that the cells surrounding the 



following confession: "The funnel is always (in the genera with a com- 

 " pact nephridium) placed to the extremity of the nephridium, though 

 "not always perhaps in actual anatomical connection with it" (1. c. p. 559). 



