PARTS CONCERNED IN REPRODUCTION. 



235 



The oviduct to complete the parallel may be compared 

 to the canal of the style in the 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. 



Corpuseules of Embryo-sac, 



[Nucleus of Archegonium,] 

 Endosperm. 



Germinal Vesicle, with Macula. 



Formative Yolk. 



[Cicatricula of Bird.] 



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. 



In regard to the homologu,es of the spermatic elements, 

 the following is suggested as on the whole the most satis- 

 factory parallel Regarding 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 



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. 



