Oligochaeta.] SUBANTARCTIC ISLANDS OF NEW ZEALAND. 271 



Notiodrilus aucklandicus, Benham. 



1903. Trans. N.Z. Inst., xxxv, p. 275. 1905. Trans N.Z. Inst., xxxvii, p. 287. 

 1907. Microscolex aucMandicus, Michaelsen, Die Fauna S.W. Austral., 

 Oligochaeta, p. 143. 



This species was originally collected by the late Captain Hutton on the Auck- 

 land Islands, probably at Fairchild's Garden, on Adams Island, which, is usually 

 visited by the Government steamer. Later, Dr. L. Cockayne brought me specimens 

 from the same spot and also from Campbell Island, and an injured specimen from 

 the Antipodes Island. During the stay of the expedition on the Aucklands I ob- 

 tained specimens from several more or less widely separated spots, enumerated 

 below ; I am therefore able to give a more detailed account of this species than 

 was possible in my former paper. 



Colour. — The general colour, when alive, is brown, though it offers variations 

 in the depth of tint — for instance, that from Disappointment Island is much paler 

 than the typical form. The preclitellar region is normally reddish-brown to sienna. 

 Those preserved in formol appear rather greyish posteriorly, owing to the intestine 

 being filled with earth, which shows by transparency through the body-wall and 

 tones down the brown tint. Those preserved in alcohol have a yellowish tint. 



Dimensions. — The length varies from 72 mm. to 118 mm.; naturally, the size 

 depends on the state of preservation, some being killed in an extended condition, 

 either well preserved and firm or ill-preserved and soft ; others are killed in a state 

 of contraction. The average length seems to be about 90 mm. to 110 mm., with 

 a diameter of 3 mm. These have about 100 segments. The number of segments 

 is not proportional to the length: thus, the greatest number is 112 for a worm 

 95 mm. in length ; the least number is 84, measuring only 72 mm., though another 

 has 94 segments in the same length of body ; while the longest specimen (118 mm.) 

 has only 108 segments. Owing to the different conditions of preservation, these 

 numbers have but little value. 



Chaetae. — Each individual chaeta is usually surrounded at its base by a pale 

 ring, so that their position is very evident in the anterior region. The chaetal 

 formula is somewhat variable, but the three intervals aa, be, dd, are essentially 

 equal ; ah is a very little less than cd, which is considerably less than be ; ab is 

 approximately equal to two-thirds aa ; the slight differences observable on careful 

 examination may be due to the differences in preservation — whether soft or firm 

 — as well as to the study of different parts of the body, as towards the hinder end 

 of the worm the intervals all become practically equal. The method followed in 

 measuring these intervals was as follows : I examined individuals from various 

 localities, cutting through the body-wall along one side and flattening out the skin 

 after removing the intestine ; the chaetal intervals were then measured with the 

 ocular micrometer. A comparison with the type, which I re-examined, shows that 

 the formula given in my paper (1903) is not correct, for I seem to have confused 

 the line of nephridiopores which occurs a little below the line of c with that line, so 

 that the formula gave be = cd. I also measured the intervals on the " round " 

 without slitting the body up ; and in other cases, as a confirmation, I measured 

 them in transverse sections. As a result of these varied measurements, I now find 

 the chaetal formula to he aa = be = dd ; ab = ed = % aa. 



