jg5 WHITMAN. [Vol. I. 



3. Questions Relating to the Nephridia. 



A few questions of a general nature remain to be considered. 

 What morphological element (or elements) represents the primi- 

 tive nephric basis? Is the non-metameric (larval) system to 

 be regarded as the main stock from which the metameric (per- 

 manent) system arises by a process of budding, as held by 

 Hatschek? Or are the relations of the two systems better 

 expressed when both are represented as buds from a common 

 stock? In either case what is the primitive form of the stock 

 itself? Is it a pair of simple cell-cords, or a pair of single 

 cells? What was the original function of these organs? 



The answers to these questions will vary according to the 

 views we entertain on the origin and significance of the meta- 

 mere and its genetic relations to the head. This problem logi- 

 cally takes precedence of the others ; but we are not yet in a 

 position to solve it, and a presentation of the leading theories 

 could not well be brought within the limits of this paper. 

 Besides, such work is rendered unnecessary by the excellent 

 review given by Fraipont (No. 34, pp. 102-125) in the latest of 

 the Naples Monographs. Bergh has recently given a compre- 

 hensive and critical review of all that is known in the compara- 

 tive morphology of the excretory organs of the Vermes (No. 

 30 and No. 21, p. 417). 1 shall therefore limit myself here to 

 a few suggestions, which appear to be warranted by the facts 

 presented in this paper, when considered in the light of what 

 was previously known on the same subject. 



Original Function. — Of the two functions now served by 

 the nephridia, which is primary and which secondary? Bergh 

 (No. 30, p. 120) holds that "die segmentierte LeibesJiohle der 

 Amieliden den HoJilen der GeschlecktsfoUikeL der Plattwiirmer 

 und Nemertincn hoviolog ist; jede H'dlfte einer ScgmeiitJiohle mii 

 dem sie begrenzenden Epithcl entspricht einem GescJilechtsfollikel. 

 Um diesen Vergleich durchzufiihren, muss man sich vor allem 

 das Verschwinden des Parenchyms bei den Anneliden verge- 

 genwartigen. Dabei legen sich die Wande benachbarter Folli- 

 kcl (Mesodermsegmente) aneinander und in dieser Weise 



(35.) Fraipont, Julien. Polygordius. Fauna u. Flora des Golfes von Nea 

 pel. Monographie XIV. 18S7. 



