Fig. 
. 
Fig. 
Fig. 
Mayer. — Staurocephalus gregaricus. 
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On 
S 
PLATE 1. 
Staurocephalus gregaricus, nov. sp., natural size, swimming near the sur- 
face of the water before the rising of the Sun. The terminal segment 
has broken off, and the genital products are escaping through tlie 
orifice. 
Staurocephalus gregaricus, natural size, showing the worm in the act of 
expelling its sexual products. The eggs or sperm escape into the 
water through the nephridial tubules, and also through rents and tears 
in the cuticula of the worm. This contraction usually occurs immedi- 
ately after the rising of the Sun. f 
Side view of the head end of the worm; magnified. (m) mouth, \- Qnwds 
Sete of the parapodia. (a) are most dorsal; (b) next; (d) next; and (ce) 
most ventral. See Figure 15, Plate 2. 
Section of an embryo in the 16-cell stage, magnified 100 diameters. Age 
3 hours. 
Section of an embryo in the gastrula stage immediately before the closure 
of the blastopore. (bp) blastopore; (sgc) segmentation cavity. Age 
94 hours. 
Longitudinal dorso-ventral section of an embryo 34 days old, magnified 
100 diameters. (an) place where the anus is destined to appear; (g/) 
head glands ; (m) place where the mouth is destined to break through ; 
(oes) cesophagus. (sf) mid gut, or “stomach.” The ege-membrane 
persists as a larval cuticula. 
Longitudinal dorso-ventral section of a young worm 16 days old. (an) 
anus ; (ds, ds, ete.) dissepiments; (g/) head glands; (m) mouth; (n) 
ventral nerve-chain ; (oes) esophagus ; (st) cavity of mid gut. 
Longitudinal dorso-ventral section through the head region of a mature 
worm, showing tentacular cirrus and muscular pharynx. The intes- 
tine of the sexually mature worm is practically empty. (m) mouth. 
(n) ventral nerve-chain. 
