300 
W. M. Wheeler 
sp mature spermatozoa. 
spc spermatocytes dividing. 
spg spermatogonia. 
spg.p spermatogonia dividing. 
st seta. 
»t.c gland'Cell wlnch secretes the seta. 
str Striated zone. 
s.v ventral body-wall. 
ts testes. 
ut »Uterus«. 
v.s vesiculae seminales. 
ver small wart-like projections of the 
dorsal Integument. 
y yellow concretions. 
z thickening in the mid'ventral line of 
ilf. platypus. 
Plate 10. 
Myzostoma cirriferum Figs. 1 — 17; M. circinatum Fig. 18; M. glahriim Fig. 19—23. 
Fig. 1. Median portion of a horizontal section through the region of the ovaries of 
a M. cirriferum 1 .25 mm long. Gundlach obj. 12/3 inch ; Zeiss oc. 3 = 100 x. 
Fig. 2 . Median portion of a horizontal section through the region of the ovaries 
of a M. cirriferum 1 mm long. Gündlach obj . 1 Vs i>ich ; Zeiss oc. 3 = 100 x. 
Fig. 3. Transverse section through the middle of the body of a M. cirriferum 
0.6 mm long. Gündlach obj. IV 3 inch; Zeiss oc. 3 = 100 x. 
Fig. 4. Transverse section through the anterior pair of ovaries of a M. cirri- 
ferum 1.75 mm long. Gündlach obj. l^/s inch; Zeiss oc. 3 = 100 x. 
Fig. 5. Median sagittal section of a M. cirriferum 1.75 mm long. Gündlach 
obj. IV 3 inch; Zeiss oc. 3 = 100 x. 
Fig. 6 a — c. Stages in the early growth of the ovum of M. cirriferum (corrosive 
subl. hardeningj. Zeiss hom. immer. V 12 ; oc. 3 = 730 x. 
Fig. 7. Five young ova of the same species, hardened in picroacetic acid. 
Zeiss hom. immers. V 12 ; oc. 3 = 730 x. 
Fig. 8. A young ovum of the same species. Picroacetic acid. Zeiss hom. 
immers. V 12 ; oc. 3 = 730 x. 
Fig. 9. Somewhat older ovum of M. cirriferum. Picroacetic acid. Zeiss hom. 
immers. Y 12 ; oc. 3 ,= 730 x. 
Fig. 10 . Ovum in about the same stage as Fig. 9. Picroacetic acid. Zeiss hom. 
immers. V 12 ; oc. 3 = 730 x. 
Fig. 11. Older ovum still showing the enlarged contours of the accessory nuclei. 
Picroacetic acid. Zeiss hom. immers. 1 / 12 ; oc. 3 = 730 x. 
Fig. 12. Young ovum with two nucleoli. Picroacetic acid. Zeiss hom. immers. 
1 / 12 ; oc. 3 = 730 X. 
Fig. 13. Older ovum with pieces of a Spermatozoon in its cytoplasm. Picro- 
acetic acid. Zeiss hom. immers. Vi 2 i oc. 3 = 730 x. 
Fig. 14. Older ovum with two nucleoli. Picroacetic acid. Zeiss hom. immers. 
V 12 ; oc. 3 = 730 X. 
Fig. 15. Mature ovum. Picroacetic acid. Zeiss hom. immers. V 12 ; oc. 3 = 730 x. 
Fig. 16. Transverse section of a M. cirriferum 0.35 mm long. Zeiss hom. immers. 
1 / 12 ; oc. 2 = 530 X. 
Fig. 17. Next section to the one represented in Fig. 16. Zeiss hom. immers. 
Vl 2 ; OC. 2 = 530 X. 
Fig. 18. Myzostoma circinatum n. sp. seen from the ventral surface. 10 X. 
Fig. 19. Transverse section through the region of the ovaries of a M. glahrum 
1 mm long and attached to the disc of the Antedon. Gündlach obj. 
12/3 inch; Zeiss oc. 3 = 100 x. 
