PLATE 4 
EXPLANATION OF FIGURES 
32. Tangential section through sperm-sac and a little to one side of the genital 
pore, a, nterus; h, sperm-sac; actual diameter of sac 0.05 millimeter. 
33. Horizontal section, a, genital pore ;/), uterus. 
34. Horizontal section, a, penis; 6, uterus; one section intervenes between 33 
and 34. 
35. Next section to 34. a, penis; h, uterus. 
36. Next section to 35. a, sperm sac; h, uterus. Figs. 33-36 are drawn to the 
same scale; the diameter of the sperm sac in 36 is 0.05 millimeter. The sections 
were at least .005 millimeter thick. 
37. Sperm sac, a, and ovum engaged in what appeared to be a kind of copulatory 
action; free hand sketch from life; e, vvisp of spermatozoa (see p. 376 for descrip- 
tion). 
38. A somewhat similar condition is here indicated to that shown in 37; from 
specimen mounted in balsam, a, sperm-sac; h, ovum with two germ cells. 
39. Empty sperm sac and ovum sketched from life; both were contracting some- 
what rhythmically, a, sperm-sac; h, ovum. 
40. Horizontal section showing the ovary- vitellarium. a, cells of ovary with the 
characteristically large germinal spots; 6, yolk-forming cells; c, uterus; d, sper- 
matozoa in duct; diameter of section 0.3 millimeter. 
41. Another horizontal section, the fifth dorsal to the one shown in fig. 40. 
fl, ovary; h, ovum with one cluster of cells showing in the section. Astudyofthe 
succeeding seccions shows that the ovum has another cluster of cells and is of the 
type shown in fig. 22. c, a nearly transverse section of a young worm. The sec- 
tion passes a little diagonally through the posterior end. Adjacent sections show 
that this is one of a pair of twins lying in their capsule, d, ciliated young with 
eye-spots. This specimen had escaped from its capsule, e, yolk-forming cells of 
the ovary-vitellarium; /, notch showing the continuation of the duct c in fig. 40, 
and continuous with the uterus of figs, 33-36. The positions of b and d were 
changed slightly to bring them within a smaller compass; breadth of section 0.3 
millimeter. 
