268 THOS. H. MONTGOMERY, 



4 below it ; the latter four were of course efferent ducts of ventral 

 longitudinal ducts. On the left side I counted with certainty 16 ex- 

 cretory ducts, 13 above, 3 below the nerve-chord ; I noticed also two 

 other structures on this side of the body, which might have been 

 excretory ducts, though I was unable to decide this point positively. 

 And just here I would observe that I examined the whole series of 

 sections with the ^/lo*^^ immersion lens of Zeiss, so that few if any 

 excretory ducts could escape me; and this examination of all the 

 sections was made twice. But it must be mentioned, that I could not 

 find these ducts at the extreme ends of the body, and that the 

 sections at these points were oblique; if excretory ducts should be 

 present here, which is not improbable, then their number might be 

 greater on each side of the body by one or two, than I found. 



A glance at Fig. 9 shows that not all the nephridia have ex- 

 cretory ducts, but that the shortest are devoid of them (these ducts 

 are represented in this figure by transverse red and green lines). The 

 number of these ducts to each nephridium, is as follows : 



Fig. 9 shows that it is the shortest nephridia which have the 

 fewest excretory ducts. We also find that the ducts of the two sides 

 are not paired; their inequahty in number on the two sides, would 

 indeed exclude the possibility of such a true bilateral arrangement. 

 The excretory pores, from those ducts placed above the nerve-chords, 

 are usually situated near the dorsal median line, not so frequently 

 more lateral. 



B. Histology. 



Terminal Bulbs. These internal terminations of the nephridia 

 may be best understood by comparing the figures: Fig. 4 shows a 

 bulb {B) in its entirety, while Figs. 2, 3, 4, 6, 7 reproduce sections. 



