134 CALIFORNIA ACAUEMY OF SCIENCES. 



Spermdncts. are coiisiderabl}' thickened, l)iit the lower part is not any thicker 

 tlian the upper part, as in B. nami. 



Gonaih are affixed higli up on the septum and not at the junction with septum 

 and body-wall. 



Prostates. These bodies are larger than in //. mimr, but nevertheless generally 

 confined to one somite cacb. The pciiial seta- areas usual, of unequal size. The 

 larger seta is i'urni.slied with four notches, the smaller is spoon-like and forked at the 

 apex. 



Nephridia. These organs are arranged in three distinct rows on either side of 

 the median line, but the nephridia in each somite are of unequal size. The nephri- 

 dium nearest the ventral ganglion or nopbridiiim n consists of two, more or less, 

 separate parts, evidentl}' a tendenov to diilnsion or an imperfect centralization. The 

 most ventral part is the smallest and the most distal the largest. The ducts run con- 

 tinuously between these parts, l)ut tlu> co'lomic cells are grouped in such a way that 

 the bridges between the two jjarts are quite narrow. The nophrostome of nopbridium 

 a was always plain and readily seen, but I never succeeded in finding the nepliio- 

 stomes of &and c. Still, these nephridia appear perfectly formed on the meganephric 

 princiiile, and I couUl never see any connection by canals between " and />, and //and 

 c, though sometimes the ca3lomic cell masses extended more or less continuously over 

 and between the respective nephridia n, h and c. 



Ncpliiidia (I open in front of setse 1 and 2, while in B. nana they open in front 

 of '■) and 1. I'bc most anterior nephridium possessing a ccelomic covering I found in 

 xxi. Tiirougii tiie courtesy of Dr. Micliaelsen, I have received specimens of B. 

 Bolnri for comparison. The nepliridium of B. pahnicola resemble that of />'. Bolari, 

 but is much larger, and the respective nephridia cover each other slightly, while in 

 the two specimens of B. Bolavi which 1 dissected the respective nephridia were sep- 

 arated by considerable distance; the latter nephridia are also smaller. I bad at first 

 intended to assign these species of Benhamia possessing several nephridia of a perfect 

 form under a separate subgenus, when my attention was called to the fact, by Dr. 

 Michaelsen, that B. Stuhhiiaiuti sometimes possessed a similar arrangement of nephri- 

 dia as those in B. Bolavi, etc." As the nephridia of B. Stnhlinnnni are generally 

 plectonephric or difTuse, it became at once evident that this distinetion emild not be 

 used as a generic character of value, and that it really is impossible to draw any dis- 

 tinct line between a plectonephric and a micronephric condition. It is, however, en- 

 tirely incorrect to characterize these nephridia as a mass of tubules, etc., as wherever 

 they are separated one from the oilier, as in Bolnri, pahnicola, nana, mgosa and 

 probably great many other species, each micronephridium is perfect in itself, and liuilt 

 on the same general principle as the meganepbridia of tiie other terricohv. T wmild 

 therefore propose to make a distinction between plectonephidia, or really dilTuse 

 nephridia, and micronephridia, or nephridia of small size, but perfect, or built on the 

 meganephric plan. Sucii a disliru-tinn maybe u.seful in descrii>tions, even if tiuy are 

 not mor|)hologically distinct. 



