383 



The author, Mr. A. G. Bourne of Madras, declares that my views on 

 the general structure of these organs are entirely erroneous. 



On the other hand, after having very carefully read Mr. Bourne's 

 criticisms and re-studied his previous publications on the subject, I 

 remain of the same opinion as before, and maintain all my views 

 and conclusions. 



Under these circumstances I feel obliged to reply to these 

 criticisms, in the interest of science; and intend to do so as shortly 

 as possible. On different points I could have contented myself with 

 reminding Mr. Bourne that positive observations always prevail 

 over negative ones or mere inductions. But on second thoughts I 

 found it better to seek out some of the causes of Mr. Bourne's 

 errors and by so doing cast a little more light on the question of 

 the nephridia. 



T. 



Let me remark, first of all, that Mr. Bourne declares he would 

 not criticise at all the cytological part of my researches. I am very 

 much obliged to him for it, as that part is by far the most important 

 of my work. 



On the other hand it is rather curious how he has been able to 

 avoid doing so, anatomy and cytology being, in these organs, so 

 narrowly bound up together that it is sometimes impossible to settle 

 the exact limits between them. 



It is quite impossible to understand the general anatomical dis- 

 position of the segmental organ without paying great attention to the 

 inner structure as well as to the very peculiar external relations of 

 their component cells. And most of Mr. Bourne's misunderstandings 

 owe their cause to the fact that he did not always pay sufficient 

 attention to the minute structure of the cells and even of what he 

 calls the lobes of the organs, as appears clearly from his descriptions 

 of C 1 e p s i n e (and Nephelis?) 



II. 



Hirudinids. 

 a) Mr. Bourne's description of the segmental organ of these 

 leeches may be summed up as follows: 

 The organ includes six different parts: 



1) A naked part beginning at the vesicle — the drain- pipe. 

 J-g. Fig. 1. 



2) A first group of cells with ramified intracytoplasmic ductules. 

 Into this main lobe enters the drain-pipe. Fig. 1 h—d. 



