ZOOLOGY. 



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

 volved in natural self-division, and it is carried on to a great 

 extent in Hydra, a mudi larger number of individuals being 

 produced in this way than from eggs. Our figure (36) 

 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 off, 

 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, all 

 the lower animals, is 

 simply due to Tan 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 Parthenogenesis or Agamogenesis is analo- 

 gous to the ordinary mode of budding. Ehrenberg first showed 

 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 



36. Hyflra fvsca, with two young (a c) bud- 

 ding from it; b. the base; f. the dige.-nvc cavity; I, 

 tentacles. From < 'lark's Mind in Nutnre 



