PLATE 2 
EXPLANATION OF FIGURES 
Nectonemertes mirabilis 
2 Surface view of a mature spermary, showing the thick layer of spiral mus- 
cular fibers surrounding the spermary proper and the epithelial wall of the semi- 
nal vesicle, the latter leading to the minute external opening on the ventrolateral 
border of the head. X 66. 
3 Optical section of a spermary, with its seminal vesicle and spermatic duct. 
The thick muscular columns (mc) of the spiral musculature surround the germinal 
cells, which oceur in all stages of development; spg, spermatogonia; spc, primary 
spermatocytes; spc’, secondary spermatocytes; spl, spermatids; spz, developing 
spermatozoa collected in bundles about the nurse cells; 0, opening from spermary 
into the seminal vesicle (sv) with its thin epithelial wall; spz’, mass of mature 
spermatozoa ready to be discharged through the spermatic duct which opens to 
the exterior by a minute pore in the basement membrane (bm) of the body wall; 
n, nuclei of muscle fibers. X 220. 
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