Oligochaeta.] 



SUBANTARCTIC ISLANDS OF NEW ZEALAND. 



287 



T)jbercvla pubertatis are present as small paired oval papillae, each with a 

 depression in its centre, at the intersegmental furrows 17/18, 18/19. These are 

 present even in specimens in which the clitellum is not developed. Further, on the 

 anterior margins of 10 and 11 there are paired 

 projections which may be also tubercula ; they are 

 in line with chaetae cd ; in one case they are also 

 on the 9th. 



There are three pairs of spermathecal pores 

 (invisible externally), at 6/7, 7/8, and 8/9, in line 

 with chaeta b. xi 



The nephridial pores, though likewise invisible, 

 are at the level of about the 15th or 16th chaeta. 



-rw// 



DiPOROCHAETA PERIONVCHOPSIR/ 



Ventral view of the genital segments. 

 (X 4.) 



Internal Anatomy. 



The posterior septa of segments 10-15 are 

 thick, especially the last four. 



There is no gizzard ; not even a trace of it is 

 recognisable in a dissected worm. The oesophagus 

 is thin-walled as it passes through 7 and 8, becomes 

 thick- walled in the 9th to 16th, then it narrows 

 in the 17th, and the intestine commences in the 

 18th as the usual wide thin-walled tube. There 

 are no oesophageal glands. 



The dorsal vessel is single ; the last heart lies 

 in the 12th segment. 



The worm is meganephric ; the coiled tubule forms a compact mass in the ventral 

 portion of the body, but the large muscular bladder passes upwards to open rather 

 above the lateral line at the level of about the 15th chaeta. 



The testes and ovaries are normal. There are two sperm-sacs, in the 9th and 

 12th. The prostate, in contrast to the form it has in the preceding species, is a 

 flattened compact mass, somewhat lobulated on its inner margin, and with a 

 quadrate outline (Plate XI, fig. 36). Its short duct arises from its under-surface, 

 and is thus invisible from above. 



Sections show that the duct contains three or more channels when it leaves the 

 gland (Plate XI, fig. 38) ; these xmite as the body-wall is approached. The sperm- 

 duct joins this prostate duct after it has left the gland, but does not enter the 

 lumen at once ; it runs alongside the three channels for some distance, and enters 

 the lumen after they have united, and, indeed, after the prostate duct has entered 

 the body-wall. The three or four channels above mentioned pass up into the gland 

 and diverge, each giving rise to a few branches as it traverses the substance of the 

 prostate (Plate XI, fig. 37) — in other words, the prostate has a character which 

 Michaelsen assigns to the genus Perionyx, and which does not occur, according to 

 his diagnosis, in Diporochaeta. 



The ventralmost chaetae, a, b, on this segment are slightly longer than the rest, 

 as 4 to 3, but scarcely deserve to be termed " penial " ; they do not differ in form. 



The spermnthecae occur in segments 7, 8, and 9. In one individual I find an 

 asymmetry, in that on one side the three spermathecae are in these segments. 



