SEXUAL GENERATION. 



683 



Fig. 221. 



tinued growth, penetrates downward through the tissues of the pistil 

 until it comes in contact with the germ below. The germ thus fecun- 

 dated, the process of generation is accomplished. The pistil, anthers, 

 and corolla wither and fall off, while the germ increases in size, and 

 changes in form and texture, until it ripens into the mature fruit or 

 seed. It is then ready to be separated from the parent stem ; and, if 

 placed in the proper soil, will germinate and produce a new plant similar 

 to the old. 



In many species of plants, the male and female organs, as above 

 described, are both situated upon the same flower ; as in the lily, the 

 violet, the convolvulus. In other instances, there are separate male 

 and female flowers upon the same plant, of which the male flowers pro- 

 duce only the pollen, the female, 

 the germ and fruit. In others still, 

 the male and female flowers are 

 situated upon different plants, 

 which otherwise resemble each 

 other, as in the willow, the poplar, 

 the sassafras. 



In animals, the female organs 

 of generation are called ovaries, 

 since it is in them that the egg, or 

 " ovum," is produced. The male 

 organs are the testicles, which 

 give origin to the fecundating pro- 

 duct, the "sperm" or "seminal 

 fluid," by which the egg is fer- 

 tilized. In the taenia or tapeworm, 

 already described (page 674), each 

 articulation contains both ovary 

 and testicle. The ovary (Fig. 221, 

 G, a, a) is a series of branching 

 tubes ending in rounded follicles, 

 and communicating with a central 

 canal. The testicle (6) is a narrower convoluted tube, closely folded 

 upon itself, and opening by an external orifice (c) upon the lateral 

 border of the articulation. The seminal fluid produced in the testicle 

 is introduced into the female generative passage, which opens at the 

 same spot, and, penetrating into the interior, comes in contact with the 

 eggs, which are thereby fecundated. Each egg then produces a young 

 embryo, which is capable of being afterward developed into a full-grown 

 tsenia. 



In various other families of invertebrate animals, as the snail, the 

 slug, the leech and the earth worm, an ovary and a testicle are both 

 present in the body of the same individual. But in these instances 

 impregnation is effected only by the concurrent action of two different 

 organisms ; and when sexual union takes place, the eggs produced by 



SINGLE ARTICULATION OF T.ENIA 

 CRASSICOLLIS, from the cat. a, a, a. 

 Ovary filled with eggs, 6. Testicle, c. Genital 

 orifice. 



