PARTS CONCERNJilD IN REPRODUCTION. 



235 



The oviduct — to complete the parallel — may he compared 

 to the canal of the stjde mthe flowering plant; while a certain 

 analogy may even be suggested between the cleavage of the 

 vitellus — giving rise to the cellular germ mass, which serves 

 as the point of origin of the embryo of the animal — and the 

 process of cell-multiplication by which is formed the suspen- 

 sor, at one of whose extremities the embryo of the future 

 plant is developed. 



The following is a tabular statement of the correspon- 

 dences now indicated ; to push them farther would be a 



matter of pure fancy : — 



Egg Structures. Seed Structures. 



Germinal Vesicle, with Macula. 



Formative Yolk. 



[Cicatricula of Bird.] 



Corpiiscules of Embryo-sac, 



[Nucleus of Ai'cliegonium . ] 

 Endosperm. 



Primitive boundary of true 

 ovum. 



Adventitious YoLk. 



Micropyle, 



Ovary and follicles. 



Oviduct. 



The Adventitious Yolk and 

 Vitelline Membrane of the 

 Bird's egg are derived from 

 the contents of the Vesicle. 



Embryo-sac, 



[Wall of Archegonium. ] 



Perisperm, 



[Canal of Archegonium. ] 



Ovule, [Fern Spore.] 



Canal of Style. 



The Perisperm and Seed- 

 coats are derived from the 

 tissue and coats of the 

 Ovule. 



In regard to the homologues of the spermatic elements, 

 the foUowino; is suo:2:ested as on the whole the most satis- 

 factory parallel. Kegarding the fovilla or contents of the 

 pollen grain as the essential spermatic element, and there- 

 fore as the equivalent of the animal spermatozoon, the 

 inner membrane of the pollen grain (intine) and its tubular 

 outgrowth may be considered as adventitious structures — 

 like the wall of the germinal vesicle — provided for the pur- 

 pose of securing the advance of the effused fovilla in a re- 

 gular column to its appointed destination, the embryo-sac 



