290 CLAYPOLE. 
EXPLANATION OF PLATE XX. 
Note. Unless otherwise stated drawings are made with Zeiss lenses and the 
ordinary tube length. Objective +5 is an oil immersion. 
Anurida maritima Guen., Figs. 1-13; stained in lithium carmine and Lyons 
blue, Fig. 14. Zomoceras sp. ? 
Fic. 1. Longisection of adult ovary in early summer.  c.e/., cephalic elonga- 
tion attached to the fat body; o., young ova; .c., nutritive cells associated with 
ova; g.é. germinal epithelium; ov., ovarian wall. Obj. 4, oc. 4. 
Fic. 2. Group of germ cells from near the germinal epithelium, showing the 
characteristic way of association. Letters as in Fig. 1. Obj. 75, oc. 6. 
Fic. 3. Ovum at later stage, when the cytoplasm is increased. Letters as 
above. Obj. +4, oc. 6. 
Fic. 4. Section of ovary in younger stage than represented in Fig. 1, yolk 
not yet appearing. .7., cytoplasm of ovum, highly vesicular; y.z., yolk nucleus 
of nutritive cells; 7, beginning of follicle. Obj. 75, oc. 4. 
Fics. 5 and 6. Transections through cephalic elongation, showing non-ger- 
minal character of cells. Obj. 75, oc. 4. 
Fic. 7. . Longisection through ovary in region of beginning of cephalic elonga- 
tion. Letters as above. Obj. 7, oc. 2. 
Fic. 8. Young ovum and nutritive cells. Letters as above. Obj. 75, oc. 6. 
Fic. g. Enlarged view of one of the small masses shown in Fig. 1. Letters 
asin 8. Obj. +4, oc. 6. 
Fic. 10. Enlarged view of an egg mass from ovary shown in Fig. I.  ch., 
chromatin; zc/., nucleolus; z., nucleus of nutritive cells and ovary; @.o., abor- 
tive ovum; y., yolk appearing in ovum. The nucleus is already invisible. Obj. 
qi) OC. 4. 
Fic. 11. Late stage of ovarian development, showing parts of two eggs. Let- 
ters as above. Obj. 7/5, oc. 2. 
Fic. 12. Final stage in ovarian development. e.m., egg membrane. Obj. 
Ta, OC. 2. 
Fic. 13. Enlarged view of abortive ovum and nutritive cell. c/., nucleolus ; 
rest of letters as in Fig. 10. Obj. 75, oc. 4. 
Fic. 14. Ovum from ovary of Thysanuran (Zomoceras), showing the begin- 
ning of yolk formation and the preservation of the group of chromosomes. Let- 
ters as before. Obj. 75, oc. 3. 
