ON THE AIORPHOLOGY OF THE EXCRETORY ORGANS 

 OF METAZOA: A CRITICAL REVIEW. 



By THOS. H. MONTGOMERY, Jr. 

 {Read April 24, 1908.) 



The desire to acquaint myself with modern ideas as to the 

 homologies of the excretory organs has led to the present review. 

 These organs constitute a chapter in comparative anatomy that is 

 one of the most compendious and intricate of all. Their relations 

 are so broad and manifold that no morphologist can go far without 

 touching upon them, and one need not wonder at this because their 

 function is above all others necessary to the continuance of the life 

 of the individual. 



Among those who have contributed largely to this subject are 

 Balfour, Bergh, Biirger, Cuenot, Eisig, Goodrich, Hatschek, Lang, 

 Eduard Meyer, Sedgwick and Vejdovsky, but the bibliography shows 

 how many well-known investigators have added to our knowledge. 

 There is a wealth of accumulated facts that have never been treated 

 critically in their entirety, and on that account the present bringing 

 together of them may be of help to future students. 



This memoir is divided into two portions: (A) a. descriptive 

 one, in which the groups of Metazoa and their particular excretory 

 organs are treated in succession; and (B) a comparative one, in 

 which all the excretory organs are reduced to certain types, and 

 then the homologies of these discussed. It is in this second part 

 that a standpoint is reached different, so far as I know, from 

 previous ones, one that I hope puts the facts in a clearer light. 



A. DESCRIPTIVE. 

 The following is a brief summary of our knowledge of the gen- 

 eral structure and embryogeny of special excretory organs con- 

 sidered separately for each group. Histological details are not 



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