THK NEPHEIDIA OF LEECHES. 549 



appears to be little short of quibble, which M. Bolsius devotes 

 to an endeavour to convince Leydig, and all who take the 

 trouble to read them, that that histologist does not now know 

 what meaning he attached to certain words written many 

 years ago, show an utter want of that feeling of regard which 

 younger histologists should entertain towards that famous 

 pioneer in our science. 



M. Bolsius prefers to use Williams' term " segmental 

 organs " for the nephridia, because this " denomination, qui a 

 pour elle I'anciennete, nous rappelle que cet organe se presente 

 dans une classe d'animaux dont le corps est compose d'une 

 maniere speciale, c'est-a-dire dans les vers." This is quite in 

 accordance with the way in which he persistently shuts his 

 eyes to all questions of homogeny : it is superfluous to discuss 

 the question at a time when so many of the best Continental 

 authors have adopted Lankester's term ''nephridia^' (Lang, 

 Eisig, and others). 



M. Bolsius' conception of the nephridium in the large leeches 

 simplifies enormously the idea of its structure, and, as he says, 

 renders it much easier to explain; though why this should be 

 an advantage if the conception is incorrect is not obvious. 



M. Bolsius says of the nephridium of the medicinal leech 

 that it is a compact organ, the two extremities of which are 

 slender, and ordinarily approach one another. Three regions 

 may be distinguished : 



(a) The superior region with anastomosing canals. 



{b) The median region with anastomosing canals surround- 

 ing a collecting or central canal. 



(c) The inferior region with a collecting canal, without 

 anastomosing canals. 



M. Bolsius then describes the cells occurring in these three 

 regions, and his figures show that, so far as the median region 

 is concerned, he recognises that the calibre of the ductules 

 increases '' a mesure qu'on descend vers I'orifice inf^rieur 

 de I'organe.'^ If this is the general view he takes of the 

 structure of the organ, no wonder that he considers that my 

 own and Schnitzels figures and description show a '' compli- 



