4 INTRODUCTION TO SEXUAL PHYSIOLOGY 



attached to the parent 

 stem and form multiple 

 .0 individuals or colonies in 

 3 the manner characteristic of 

 sponges and corals. Among 

 the higher plants also pro- 

 pagation may take place by 

 budding as well as by the 

 sexual method. 



Allied to the process of 

 budding is that of the 

 regeneration of lost parts 

 of the organism or of struc- 

 tures submitted to injury. 



Fig. 2. — Longitudinal section 

 through Hi/dra^ magnified 

 (diagrammatic). 



(From Shipley and MacBride's 

 Zoohxfij^ Cambridge Uni- 

 versity Press.) ], Mouth; 

 2, foot ; 3, tentacle ; 4, di- 

 gestive cavity ; 5, ectoclei'm 

 or outer layer of cells ; 6, 

 endoderm or inner layer ; 

 7, intermediate structureless 

 lamella ; 8, batteries of 

 thread cells used for killing 

 prey ; 9, testis ; 10, ovary 

 with ovum. 



This power is possessed in 

 some degree even by the 

 higher animals, as with the 

 limbs of a newt or sala- 

 mander which grow again 

 after being destroyed. 

 Among some of the lower 

 forms of life, however, com- 

 plete individuals may be 

 regenerated, as when a flat 

 worm is divided into a 

 number of pieces each of which can develop into a new individual. 

 Conjugation. — It has been mentioned that sexual reproduction 



