14 IVAR ÅRWIDSSON, SYSTEMATIC NOTES ON SOME MALDANIDS. 



There are altogether (normally) 19 setigerous segments, observed in all the 9 com- 

 plete individuals suitable for an investigation of this sort. The segments situated be- 

 hind the 8 th setigerous segment are considerably elongated and it is not until the 18 th 

 — 19 th setigerous segments that the decrease in length begins. The number of achae- 

 tous segments is 5 (fig. 12); they are followed by a short, somewhat shining part (not 

 quite re-developed in fig. 12 af ter previous mutilation), whose posterior margin supports 

 the anal cirri. Finally we come to the posteriorly projecting, strong anal cone, which 

 in certain states of contraction passes directly into the cirrus-bearing margin, but in 

 others is surrounded by a deep forrow inside the same margin. 



Of the anal cirri, which according to Mc Intosh number 5—7, the middle ventral 

 one is the longest (figs. 12 and 13). Of distinct lateral cirri I found 1 pair on each side 

 at most ; ef. fig. 13, which also shows a faint swelling just below the longest lateral cirrus 

 of the right side, corresponded to on the other side by a similar one. Dorsally of each of 

 these longer lateral cirri there is a somewhat shorter one situated not quite halfway to 

 the middle line. The specimen in question, like all the individuals investigated, has the 

 posterior end more or less completely regenerated. One individual has 3 lateral cirri, 

 2 on the left close together (the upper one shorter than the lower one), and 1 on the right, 

 occupying about the same position as the upper ones in the preceding specimen. Of the 

 other 11 posterior ends investigated 10 have 1 cirrus on each side (ef. fig. 12), but the 

 ll th , which is very weakly regenerated, has only the ventral cirrus, which is moreover 

 very short. One very slightly regenerated posterior end among the others shows, how- 

 ever, 1 cirrus on each side. As a rule the l st pair of lateral cirri are re-developed very 

 early (ef. p. 9). 



Nephridia are found on the 6 th — 10 th setigerous segments and their orifices are 

 situated distinctly behind the lowest uncini. 



A large number of anomalous specimens were observed, which can be divided into two groups. 

 All these specimens have a lower glandular field on the 3 rd nephridia-bearing segment (normally 

 the 8 th setigerous segment) and behind this segment 2 nephridia-bearing segments; no extra nephri- 

 dia-bearing segments have been observed, i. e. even in these specimens there are nephridia only on 5 

 segments (6 th — 10 th normal setigerous segments) throughout. One group of these divergent specimens 

 is characterized by a more or less complete triangulär lower glandular field even on the 9 th setigerous 

 segment, or indications of such a one; an indication of corresponding dorsal anterior converging gland- 

 ular spöts was also observed in one case. Thus 1 specimen from Balloch Sands (I in Table p. 15) 

 has this extra lower glandular field almost complete; posteriorly, however, its sides are different, 

 only its left side reaching the parapodium, and, as a matter of fact, even here only partly. 2 other 

 specimens from the same locality each have in front of the rows of uncini of the 9 th setigerous seg- 

 ment (in one case in the middle of the row, in the other obliquely below) a small round glandular spöt. 

 Finally a more distinct beginning of a glandular field like that of the first-mentioned specimen is seen 

 in a specimen from Millport, which has two rather considerable glandular spöts, somewhat different 

 in size, on the lower side of the 9 th setigerous segment in front of the parapodia; the specimen has 

 the left nephridium of the 6 th setigerous segment strongly reduced with no visible orifice. 1 speci- 

 men from Great Cumbrae Island has about 8 glandular spöts of different size which constitute re- 

 mains — still distinct — of a lower glandular field on the 9 th setigerous segment; here there are also 

 weak beginnings of the anteriorly converging glandular band of the dorsal side. 



