546 REVIEW. 



greater detail than I attempted to do ; and had he been able to 

 correct here and there errors in my results I should not have 

 been surprised, or should at any rate have been content to 

 leave future observers to judge between us. 



It is, however, not a question of occasional errors ; M. Bolsius 

 has entirely misinterpreted his sections, or else I, to say nothing 

 of my predecessors, evolved a conception of these organs out 

 of my inner consciousness. 



I am induced to review the matter in some detail, in order not 

 merely to defend my views in all important particulars, but to 

 point out that what I believe to be M. Bolsius' errors in fact 

 are due to errors in method ; that they are owing, in short, to 

 his abuse of the very methods which should have (which have 

 in many respects) helped him. 



It is quite clear that whatever value attaches to M. 

 Bolsius^ voluminous productions depends upon the new facts 

 tlierein set forth. Phylogenetic or homogenetic considerations, 

 or, indeed, generalisations of any sort, M. Bolsius studiously 

 avoids. He naively remarks, it is true, in the introduction 

 to his first paper, that ''segmental organs" are not confined 

 to the leeches, but are found in all Annelids; and, further, 

 that certain organs, which are described as their homologues, 

 are found in animals occupying various positions in the animal 

 scale up to the Vertebrates themselves (" jusqu'aux Vertebres 

 eux-memes '^). If I appreciate the exact force of these last 

 words they display a curious conception of the animal genea- 

 logical tree. 



Now M. Bolsius' facts fall under two headings, cytological 

 facts and anatomical facts. With the former I here concern 

 myself little, but 1 have not the slightest hesitation in saying 

 that all his most important anatomical results are absolutely 

 erroneous. 



I attribute M. Bolsius' errors to the abuse of a method. M. 

 Bolsius, however, takes great credit to himself over his choice 

 of methods; his latest publication (4) commences thus: — 

 " Pour arriver k un but sans trop s'exposer h faire fausse 

 route, il faut prendre les raoyens les plus propres k cette fin. 



