2 74 MENSCH. [Vol. XVI. 



separated stolons, or the so-called sexual individuals, Polybostri- 

 cus {t) and Sacconereis (9). The Polybostricus of the red 

 variety (PI. XIII, Fig, 3) is about 5 mm. long ; that of the 

 green variety, 4 mm. and more slender. (This and the color 

 being the only marks of distinction between the two varieties, 

 I shall make no reference to either variety in further descrip- 

 tions.) It consists of from eighteen to twenty-four setigerous 

 segments, the first three of which have short parapodia, with 

 short setae similar to those borne by the parapodia of the 

 parent stock (PI. XIII, Figs, \a. and lb), and contain the sex- 

 ual products. All the segments posterior to these, with the 

 exception of the last or anal segment, have large elongated 

 parapodia (PI. XIII, Fig, 4), consisting of a ventral less mus- 

 cular portion ending in a short process (^'.r.) and bearing the 

 short setae, and a more dorsal thickened and very muscular 

 portion ending in a process (d.r.) which contains a tuft of long 

 swimming setae. Dorsal to the thick musculature belonging 

 to the dorsal ramus is a thin plate-like structure which forms 

 the dorsal outline of the parapodium and constitutes the basal 

 portion of the dorsal cirrus (d.c). When the stolon is at rest 

 the parapodia are always directed backward and pressed close 

 against one another, thus giving this part of the body a very 

 compact appearance and obscuring the outline of the segments. 

 The size and direction of these parapodia as compared with the 

 size and direction of the three anterior pairs produce a contrast 

 sufficient to divide the stolon into two well-marked regions. At 

 the junction of these regions the body-wall, consisting of the 

 posterior part of the third and the anterior part of the fourth 

 setigerous segments, shows quite prominently, and on exami- 

 nation appears less firm, and the line of demarcation between 

 the segments is much fainter than it is in the parent stock. 

 The anal segment is small, considerably narrower than the 

 preceding segments, and in place of parapodia a pair of long, 

 slender caudal cirri form the only appendages of the segment. 

 The buccal segment is well marked and bears a dorsal and a 

 ventral pair of tentacular cirri. The dorsal tentacular cirri (d.t) 

 are very stout at the base and, when fully extended, reach as 

 far back as the thirteenth or fourteenth setigerous segments. 



