MAYER: STAUROCEPHALUS GREGARICUS. 5 
elongate hypodermis cells. The first metamere back of the head 
usual}y 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 setz. 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 (4, Figure 4). The ventral half of the setigerous 
lobe bears five or six setze of the sort shown in d, 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 more 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 
Nereidz 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-red 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 larve were killed in Perenyi’s fluid, 
stained in Kleinenberg’s hematoxylin, imbedded in paraffin and 
sectioned, the sections being usually of about 6.6 yw in thickness. 
