236 HOMOLOGICAL RELATIONS OF THE 



of the ovule,* and may be regarded as homologous with 

 the vesicle of evolution, whose nucleus in most animals be- 

 comes the spermatozoon. On this supposition the pollen 

 grains would correspond to the parent cells within which 

 the " vesicles of evolution" are generated, while the primary 

 cells of the anther would represent the tubules, follicles, or 

 other secreting cavities of the spermatic gland — relations 

 which may be expressed in a tabular way, as follows : — 



Animal Structures. 

 Vesicles of evolution and 



Spermatozoa. 

 Spermatic parent cells. 

 Seminiferous tubules, folli- 

 cles, &c. 

 Anther. I Spermatic gland. 



On the same principles the corresponding relations of 

 the opposite sexual elements may be represented as fol- 

 lows : — 



Vegetable Structures. 

 Pollen-tube and Fovilla. 



Pollen grain. 



Primary cells of Antber. 



Animal Spermatic. 



Vesicles of evolution ) 



and Spermatozoon. ) 

 Parent Sperm-cell 

 Spermary and follicles. 



Animal Germinal. 



Germinal vesicle 



and Macula. 

 Ovum. 

 Ovary and Ovisacs. 



* Danvin notices another provision for a like object in the long probos- 

 cidiform introraittent organ of some of the " parasitic males" among the 

 Cii-ripedia. Speaking of this organ in Cryptophialus minutus, he re- 

 marks that its use " obviously is that the spermatozoa of these males, 

 which are so extremely small in size, compared to the female, should all 

 be conveyed within the sac, and none be lost. It should be borne in 

 mind that the whole male, including every part, is scarcely larger than a 

 single ovum, of which sometimes sixty have to be impregnated by only 

 two or three males." The spei-matozoa, he goes on to observe, have to 

 pass a distance of about l-7th of an inch from the gland to the lower 

 ova — but of this about two-thirds would be along the canal of the intro- 

 mittent organ (Monograph, II., 586). The envelopes of the female germ, 

 in the Phq,nerogamia and Cryptogamia respectively, have already fur- 

 nished us with a parallel case of the application of organs of very different 

 homological import, to the discharge of similar functions. 



