v REPRODUCTION 307 



been tried of cutting the living animal into pieces, 

 each of which was found to undergo regeneration into a 

 perfect individual (compare p. 268). 



The sexual organs or gonads (p. 193) are of two kinds, 

 spermaries and ovaries. Both are found in the same 

 individual, Hydra being hermaphrodite or monoecious. 



The spermaries (Figs. 75, B, and 76, A, spy) are 

 white conical elevations situated near the distal end 

 of the body : as a rule not more than one or two are 

 present at the same time, but there may be as many as 

 twenty. They are perfectly colourless, even in the green 

 and brown species, being obviously formed of ectoderm 

 alone. 



In the immature condition the spermary consists of a 

 little heap of interstitial cells covered by an investment 

 of somewhat flattened cells formed by a modification of 

 the ordinary large cells of the ectoderm. When mature 

 each of the small internal cells becomes converted into 

 a sperm (p. 194), consisting of a small ovoid head 

 formed from the nucleus of the cell, and of a long 

 vibratile tail formed from its protoplasm (Fig. 76, G). 

 By the rupture of the investing cells or wall of the 

 spermary the sperms are liberated and swim freely in 

 the water. 



The ovaries (Figs. 75, B, and 76, A, ovy) are found 

 nearer the proximal end of the body, and vary in 

 number from one to eight. When ripe an ovary is 

 larger than a spermary, and of a hemispherical form. 

 It begins, like the spermary, as an aggregation of 

 interstitial cells, so that in their earlier stages the sex of 

 the gonads is indeterminate. But while in the spermary 

 each cell is converted into a sperm, in the ovary one 

 cell (Fig. 76, A, ov) soon begins to grow faster than the 

 rest, and becomes amoeboid in form, sending out 

 pseudopods amongst its companions and ingesting the 



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