Beniiam. — Earthworms from Stephen Island and D'U rville Island. 35 



Octochaetus thomasi BecUlard. 



Three individuals of this common South Ishand species were included in 

 the collection from Stephen Island. 



Maoridrilus tetragonurus Michaelsen. 



This handsome species is evidently tolerably common on Stephen Island, 

 as Michaelsen obtained four specimens. Ude speaks of several, and Dr. 

 Thomson sent me seven individuals collected during his brief visit. 



The largest specimen in this last gathering measures 210 mm. in length, 

 which is not so long as those described by Ude, which attained as much 

 as 280 mm. 



I have nothing to add to the two accounts given by these two zoologists. 



M. megacystis n. sp. 



A single specimen of a small worm measures 90 mm. in length, with a 

 diameter of 5 mm. ; but it is poorly preserved, so that its dimensions are 

 not accurately indicated by these figures. 



Its colour is greyish-purple when preserved, and the clitellum has a 

 redder tone. 



The clitellum is fairly well marked over segments 14-22 : that is to say, 

 the segments themselves are glandular, but the intersegmental furrows still 

 remain distinct. 



The chaetae have the arrangement usual in the genus : the spaces aa, 

 he, and dd are practically equal, though aa is rather less than dd or he — at 

 any rate, behind the clitellum. Owing to the softness of the worm, it does 

 not show the squareness of the tail which is f o common in the genus. 



Porophores are but feebly developed, and the ventral region of the 

 segments 17 and 19 between the porophores is depressed so that in the 

 18th segment a slight transverse pad is left on the ventral surface. The 

 spermatic grooves are convex mesially. and lie mediad of the ventral 

 chaetae, which are quite distinct here, and are not thrust out of line of 

 those in the neighbouring segments (as are those in the next species). 



Internal Structure. — The septa separating the segments 8-14 are more 

 or less thickened. 



The dorsal vessel is single throughout the worm ; the last heart is in 

 the 13th segment. 



The gizzard lies in the 6th. This is its true or " morphological " posi- 

 tion, but, as is usually the case, it gets pushed backwards owing to the 

 fact that the preceding region, like the gizzard itself, is longer than the 

 segments to which it belongs. 



There are large oesophageal glands in the 15th and 16th segments, and 

 a smaller pair in the 14th. They are subspherical dilatations of the tube 

 on each side, and the anterior two pairs meet their fellows above the gut. 



The reproductive organs li' in the usual segments and in their normal 

 positions. 



Each spermatheca (fig. 1) has a relatively enormous diverticulum, which 

 is as large as the ampulla — so large, indeed, that at first one thinks there 

 are four spermathecae. The diverticulum, further, is not racemose, as usual, 

 but has a smooth wall and a nearly globular form. When mounted, how- 

 ever, and viewed under the microscope one can see the outlines of the 

 characteristic chamberlets into which its cavity is divided ; but these walls 

 do not affect the surface. 



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