270 DISCOVERY REPORTS 



Internal characters. Lateral hearts three pairs in segments 10-12, not five pairs in 

 segments 9-13 as described for the types. Intestine apparently without trace of 

 typhlosole. Nephridia with large terminal vesicles. Seminal vesicles two pairs in 

 segments 11 and 12 as described for the types; the so-called median ventral seminal 

 vesicle described by Beddard appears to be merely a thin-walled sub-oesophageal 

 coelomic chamber. Ovisacs present, moderately large. 



The prostates usually extend back through 3-5 segments; in one specimen the 

 anterior prostates were very reduced and only occupied one segment. The duct is 

 confined to the first prostatic segment and is moderately long and coiled ; near the gland 

 it is very thin, but the ectal half is thicker and muscular. The gland is thick, tubular and 

 irregularly bent, occupying the remaining 2-4 prostatic segments. 



The penial setal sac muscles originate from the body-wall of the segment in which 

 they lie. Penial setae of two sorts, as originally described by Beddard. The dimensions of 

 fully grown setae from both the a and b bundles are about the same (length ca. 1-5 mm., 

 maximum diameter near the base ca. 38 /x, in middle of stem zj-^fi, at distal end just 

 below point where seta begins to taper abruptly ca. ii-i2jli). In both the stem is 

 almost straight, and tapers to a filiform point. In the a setae the distal end is spirally 

 curved through about i-i J revolutions, the direction of the spiral is the same as that of 

 the ornamentation described below. In both setae the distal end of the stem is orna- 

 mented, but the type of ornamentation differs. In the a bundle (Fig. i h, i) the 

 ornamentation begins with single, more or less regularly placed teeth around the stem, 

 these give place to a spiral row of about thirteen scalloped knobs which pass up nearly 

 to the point where the seta begins to taper and then stop abruptly ; the distal extremity 

 beyond this is ornamented with a few very fine teeth. The spiral line of knobs completes 

 one extended revolution; in setae from the right side the spiral is clockwise, in setae 

 from the left side it is anti-clockwise. In the b bundle (Fig. i k) the distal part of the 

 stem, almost up to the point where the seta begins to taper, is ornamented with more or 

 less regularly placed single or double teeth; these setae are presumably identical with 

 the "smooth" type described by Beddard, since the a setae agree with his description 

 and figure of the knobbed type. In Beddard 's figure the extreme distal end of both types 

 of setae is shown to terminate in a round knob ; in all specimens examined by me the 

 distal end is filiform as described above. Such a knob was occasionally observed in the 

 rather similar penial setae of the b bundle in M. georgianns. In a juvenile specimen the 

 precursory penial setae (Fig. i i, j) were found to be more or less of the adult type but 

 shorter, more slender and with less pronounced ornamentation. 



The spermathecae are very similar to those of M. georgianus with two unstalked 

 narrowly pear-shaped diverticula, and a somewhat larger pear-shaped ampulla passing 

 gradually into a stout duct which receives the diverticula. 



Paired septal organs occur, as described by Beddard, from about septum 23/24 back- 

 wards ; they usually hang backwards into the segment behind, but may occasionally 

 project forwards instead; the size is very variable. 



The internal characters are otherwise in agreement with those specified for the types. 



