CONJUGATION 



143 



analogous to the fertilisation of a passive ovum by an active sper- 

 matozoon. In Volvox this is even more obvious, for the small and 

 active cells, both in shape and method of formation, recall the sper- 

 matozoa of higher forms. 



Significance of Conjugation. — Conjugation is an episode in repro- 

 duction, not a mode of multiplication. It promotes variability in a 

 stock and it helps to ward off senescence. All the descendants of a 

 single individual form what is called " a pure line," and conjugation 

 does not occur among the members of a pure line. Asexual multiplica- 

 tion may continue in ideal conditions for ten years and through thou- 



FiG. 66. — Spore-formation in Noctiluca. — After Roule- 



From minute nucleated hillocks on the surface 

 of the cell peculiar flagellate spores (SP.) are 

 given off. The long flagellum becomes the 

 short oral flagellum of the adult. The peak- 

 like process develops into the large locomotor 

 flagellum of the adult (see Fig. 65). 



sands of generations. In ideal conditions of experimental isolation 

 there is no falling off in the vigour of the stock. But in such cases, 

 as also in certain species of Paramoecium in natural conditions, there is 

 a periodic, approximately monthly occurrence of a process called by 

 Woodruff and Erdmann " endomixis." There is a nuclear disintegra- 

 tion, followed by reintegration. It is similar to the preliminary stages 

 leading on to conjugation, but no conjugation occurs. Endomixis is 

 a process that assists rejuvenescence. 



Ecology. — Many Protozoa raise organic debris once 

 more into the circle of life, and many form part of the food 



