MAYER: STAUROCEPIIALUS GREGAlilCUS. 5 



elongate hypoderrnis cells. The first metaraere back of the head 

 usually bears a pair of very rudimentary parapodia, each consisting of 

 but a short dorsal and ventral cirrus. (Figures 11, 12.) In the worm 

 shown in Figure 3, Plate 1, the first three segments back of the head 

 bear very minute and undeveloped parapodia. The parapodia of the 

 body segments are all similar each to each and consist in a well-developed 

 dorsal cirrus, a central setigerous lobe, and a ventral cirrus that is 

 shorter than the dorsal. (See Figure 13, Plate 2.) The setigerous lobe 

 bears four kinds of setae. Most dorsal of all are three or four long 

 curved, slender bristles having a delicately serrated edge (a, Figure 4, 

 Plate 1). Immediately below these there are three or four smaller and 

 more slender bristles, having flat spatula-shaped distal ends that 

 exhibit sharp serrations (Jj, Figure 4). The ventral half of the setigerous 

 lobe bears five or six setae of the sort shown in (/, Figure 4 ; and most 

 ventral of all there is a single thick, stiff bristle c, Figure 4. The 

 blood of the worm is red, and there is a large red-colored blood sinus at 

 the base of the dorsal cirrus of each parapodium. (See Figure 13.) 

 The 25-30 anterior segments contain no sexual elements, these being 

 found, however, in all of the moi'e posterior segments. The blood 

 vessels and nephridia of the sexually mature segments are much larger 

 than are the corresponding organs in the anterior segments. The 

 nephridia of the sexual segments evidently serve to carry off the eggs or 

 sperm. The nephropores {np. Figure 13) are found at the base of 

 each parapodium near the ventral surface. Sections of the worm were 

 made, but the histology is so closely similar to that of other well-known 

 Xereidse that we consider it unnecessary to enter into details concerning 

 it. The constriction of the sexual segments is due to the powerful 

 contraction of the circular muscles that lie immediately beneath the 

 hypodermis. The sexes are separate, and there is no distinctly marked 

 sexual coloration. The general color of the worm is dull brick-i'ed or 

 ochre-red, and there is a row of diamond-shaped dull white spots, one 

 in each metamere, running down the mid-dorsal line (see Figure 10, 

 Plate 2). Dark brown pigment is found around the orifice of each 

 nephridium {np, Figure 13), and there are some indistinct brownish 

 spots on the ventral side of the head (see Figure 12, Plate 2). These 

 are not found, however, in all individuals, and probably do not function 

 as eye-spots. 



Development. — The eggs and larva3 were killed in Perenyi's fluid, 

 stained in Kleinenberg's ha^matoxylin, imbedded in paraffin and 

 sectioned, the sections being usually of about G.6 /* in thickness. 



