54 



ZOOLOGY. 



The process of budding is but a modification of that in- 

 Tolved in natuial self-division, and it is can-ied on to a great 

 extent in llydra, a much larger number of individuals being- 

 produced in this way than from eggs. Our figure (3G) 

 shows two individuals budding out from the parent Hydra ; 



the smaller bud (a) is 

 a simple bulging out 

 of the body- walls, the 

 bud enveloping a por- 

 tion of the stomach, 

 until it becomes con- 

 stricted and drops ofP,. 

 the tentacles mean- 

 while budding out 

 from the distal end, 

 and a mouth-opening: 

 arising between them, 

 as at c. Budding in. 

 the Hydra, the Acti- 

 nia, and, in fact, alt 

 the lower animals, is- 

 simply due to an in- 

 crease in the growth, 

 and multiplication of 

 cells at a special point 

 on the outside of the 

 body, while the asex- 

 ual mode of reproduc- 

 tion in the Aphis and 

 a few other insects 

 results from the mul- 

 tiplication of cells at 

 a particular point (the 

 ovary) in the inside of 

 the body. Thus Parthenugenesis or Ayamogenesis is analo- 

 gous to the ordinary mode of budding. Ehrenbergfirstshowett 

 that the Hydra reproduces by fertilized eggs. Kleinenberg 

 describes the testis, which is lodged in the ectoderm, and 

 which develops tailed spermatozoa like those of the higher 



Fig. 36 —Hy'^ra finca. with tr-o yonng (a c) bnd- 

 jling frouT 11; d. ilic bu.-c; ». tlic disjesuve caWty; t^ 

 teutacles. — Froiu ('lurk's Jfiiid iii Kuturc 



