IOO EDWARD DRANE CRABB. 



^^1 PLATE 2. 



Free ova from the hermaphrodite apparatus of three different individuals. 

 Figs, ii and 13-16 are from the same snail. Scale, 0.03 mm., PI. 4, except 

 Figs. 8-10. 



FIG. 7. A single section of an ovum, from an acinus, which is entirely 

 free from the hyaline membrane and shows high polyspermy, Modified 

 Flemming, 8 M, iron-hsematoxylin. 



FIG. 8. A young sperm head which has just loosened its hold on a Sertoli 

 cell. Much enlarged. 



FIG. 9. A ripe conoid sperm head from an acinus. Much enlarged. 



FIG. 10. A round-head sperm from the hermaphrodite duct. Much en- 

 larged. 



FIG. ii. An ovum from the hermaphrodite duct, reconstructed from three 

 sections ; supernumerary sperm heads omitted. Zenker, 40 C., 7 M, iron- 

 hsematoxylin, eosin. 



FIG. 12. A free ovum nearly surrounded by the hyaline membrane with 

 forming first maturation spindle, three sperm heads and a structure which 

 may be an abnormal sperm pronucleus and which was transposed from the 

 next section. Modified Flemming, 8 n, iron-haematoxylin. 



FIG. 13. An ovum from the hermaphrodite duct, reconstructed from five 

 sections which are consecutive except that one is missing. Zenker, 40 C., 

 7 /", iron-hdematoxylin. 



FIG. 14. An ovum from the same slide and region as Fig. 7 showing 

 degenerating (?) supernumerary sperm amphiasters and numerous large 

 yolk granules. All structures, except the two central clear areas, are from 

 one section. 



FIG. 15. An ovum from the hermaphrodite duct, reconstructed from three 

 consecutive sections showing a supernumerary aster (archiaster), early first 

 maturation spindle (" archiamphiaster," Mark, '81), and several disin- 

 tegrating sperm heads which occurred on a single section. Same slide and 

 region as Fig. n. 



FIG. 16. An ovum from the hermaphrodite duct, reconstructed from six 

 consecutive sections. Three sperm archiasters and seven heads are all from 

 the same section. The archiamphiaster may be shown too long. Zenker, 

 40 C., 7 M, iron-haematoxylin, eosin. 



