280 Transactions. — Zoology. 



exists in Maoridrilus and other Acanthodrilids, but the de- 

 pression is limited laterally by a slight ridge just lateral of 

 the porophores. 



The spcrmathecal pores, between segments 7/8 and 8/9, 

 are in line with the ventralmost couple of chaetas. 



The nephridiopores , large and conspicuous, alternate in 

 the greater part of the body (as I showed in 1892), being 

 usually in front of the 4th and the 10th couple of chaetae, 

 counting from below. 



As will be seen below, the internal anatomy presents de- 

 finite distinctive features in these two species. 



P. sylvestris, Hutton. 



The prostomium is " epilobic " — i.e., it is prolonged back- 

 wards, or imbedded in the 1st segment for about two-thirds 

 of its length (see Hutton's fig. E). 



The clitellum in some of the specimens does not extend 

 beyond segments 14 to 17, but in the type itself, as well 

 as in the specimen named "punctata," it intrudes upon the 

 18th segment ; and in another local specimen 1 note that it 

 commences in the 13th. Possibly, therefore, when fully 

 developed it covers the six segments — 13 to 18. 



Copulatory tubercles are present — at any rate, in some of 

 my specimens — in the form of transverse oval glandular areas 

 extending across the ventral surface of segments 11 and 12. 



Of internal organs the following appear to be of diagnostic 

 value : — 



The dorsal vessel is double up to the loth segment ; the 

 two vessels lie close together, and in my account of P. punc- 

 tata I figured the vessel as single. It is, however, distinctly 

 double in the intestinal regions. In the 14th segment the 

 two canals still exist, but are bound together in one coat ; 

 in the 13th the fusion is complete, and a single vessel runs 

 forwards. 



There are three pairs of hearts, the last being in the 12th 

 segment. 



There is no gizzard recognisable on dissection. The 

 oesophagus bears a pair of large glands in the 14th seg- 

 ment, and frequently these protrude into the 13th ; indeed, 

 in one case this portion was constricted off so as to form 

 a small and apparently independent gland. The intestine 

 commences in the 16th segment. 



With regard to the reproductive system, there are four 

 pairs of sperm-sacs even in the tj^pe, notwithstanding my 

 statement (1898, p. 162) to the effect that there are only 

 three pairs. My laboratory note, as well as a re-examina- 

 tion of the type, gives four as the true condition, as I 

 described in 1892 for punctata. 



