278 EXPLANATION OF THE PLATES. 



a pollen tube d, passing down from tlie micropyle c, through 

 the tissue of the nucleus a, to the enibryosac 6, whose summit is 

 occupied by protoplasmic masses e, one of which on impregna- 

 tion developes the embryo. 



Fig 8. — Embryogeny of Orchis Morio (from Henfrey), a the 

 pro-embryo formed from the upper of the two cells, into which 

 the germinal body divides on impregnation, but, unlike the 

 suspensor of the Coniferse, growing upwards into a blind fila- 

 ment, which projects through the micropyle ; h the true embryo, 

 produced by the sub-division of the lower of the two primary 

 cells. 



Animal Embryogeny. 



Fig 9. — Part of the egg of Musca vomitoria (from Meissner), 

 showing the micropyle occupied by a cluster of spermatozoa — 

 (pp. 69-70). 



Fig. 10. — Ovum of Unio (from Hossling), in which the aper- 

 ture of the hollow pedicle serves the purpose of a micropyle — 

 (pp. 69.70). 



Figs. 11-13. — Successive stages of the cleavage of the yolk, 

 after impregnation in the Mammalian ovum (from Kirkes) — 

 (p. 72). 



