VEGETATIVE PROPAGATION 



321 



acteristic of the adult. This comparatively simple life -history 

 appears to be a good illustration of the Law of Recapitulation, 

 of which mention has already been made in this work. Other- 

 wise expressed, the development of the individual epitomizes in 

 a more or less perfect way the evolutionary history of the group 

 to which the individual belongs, recapitulating ancestral stages. 

 It is generally held that these suctorial Animalcules are an off- 



D4 D5 De D7 



Dio 

 (?) 



D11 



Fig. 846. — A Spore-forming ..nimaicule [Colpoda], greatly enlarged 



A, Free-swimming individual, b and c, Encystment followed by division into two and four respectively. D i-D 3, 

 Encystment and Spore-formation; D4-D 14, development of a spore, f. Food, /.z'. , pulsating \'acuole. 



shoot from the ciliated group in which such forms as the Slipper- 

 and Bell-Animalcules are included. And the existence of a ciliated 

 stage in the life-history is not improbably reminiscent of ancestors 

 in which cilia were present throughout life. 



Spore-formation. — In the examples selected to give some idea 

 of the nature of fission we saw that the body of the parent divided 

 into two parts only. But many cases are also known of nmltiple 

 fission, where several rapid divisions take place in succession, as 

 a result of which several new individuals are brought into exist- 

 ence. In the Bell- Animalcule and its allies, for example, it often 

 happens that a large fixed individual undergoes rapid unequal 



