30 THE SHORTER SCIENTIFIC PAPERS 



Harvard University, in the loan of literature otherwise 

 inaccessible. I am furthermore greatly indebted to Sam- 

 uel Henshaw of the Museum of Comparative Zoology for 

 noting certain references. 



The studies of the various species were made primarily 

 from living specimens, all figures having been drawn with 

 the aid of the camera lucida at the magnification noted in 

 each instance. The most satisfactory method was that 

 of transferring the Naid from the culture by means of a 

 pipette to a watch-glass and subsequently to a drop of 

 water on a slide, then placing over the drop a cover-glass 

 the margin of which was supported by an extremely thin 

 wooden wedge. After a time the specimens, without un- 

 due compression, would become quiet and outline draw- 

 ings could be made with the camera. Specimens to be 

 mounted were fixed with hot sublimate-alcohol (sub- 

 limate 10 g., absolute alcohol 100 cc, distilled water 100 

 cc, acetic acid 2 cc.) , stained in borax-carmine, and 

 eventually transferred to balsam, while those sectioned 

 were stained in hsematin I A (Apathy) or in iron-hasma- 

 toxylin (Heidenhain) after fixation in cold sublimate- 

 alcohol. The index of refraction of balsam approaches 

 so closely the refraction of the transparent setx that in 

 order to study them most advantageously it was found 

 advisable to kill the specimens by compressing them under 

 the cover-glass and then at once to make camera lucida 

 drawings of the setae in the dorsal and ventral bundles. 



The Naididas are distinguished from the other families 

 of the Oligochasta primarily by the fact that their normal 

 method of reproduction is by means of budding, and that 

 complete intersegmental dissepiments are present. The 

 closely allied family ^olosomatid^e are without dissepi- 

 ments and are usually of much smaller size. Furthermore, 

 the presence of colored "oil drops" together with the 

 absence of biuncinate setae are characters which as a rule^ 

 will serve to distinguish these families. The Enchytrae- 

 idse may be separated by the absence of biuncinate setae, 



■"^Colored oil drops are absent in JEolosoma beddardi, Molosoma niveum from 

 North America, and two species of Pleurophleps occurring in Ceylon and Central 

 America. 



