FOUNDATIONS 19 



In botany its motor organs are termed cilia, in zoology 

 flagella. There is no essential difference between the organ 

 indicated by cilium (eye-lash) and flagellum (whip-lash), 

 but it is useful to use words to distinguish the single or few 

 motor organs of the Flagellata from the relatively smaller 

 and more numerous organs of the Ciliata. In this book the 

 word flagellum will be used for motor organs of the zoo- 

 spores of algae, and Phycomycetes, <fcc., where " cilium " is 

 usually written. 



Difference in the use of terms is nowhere more marked 

 than in the use of the word " spore." In zoology it is now 

 but little used : asexual reproductive elements are merozoits 

 to distinguish them from sexually formed sporozoits. What 

 used to be called a spore in gregarines is now a sporocyst, and 

 its contents sporozoits. In Myxosporidia and Haplosporidia 

 the first subdivisions are pansporoblasts, which produce the 

 sporoblasts or spores. Pansporoblasts with many minute 

 spores recall the sporangia, which are grouped in the sorus 

 of synchytrians. 



In botany there is need of names for a wide range of 

 reproductive elements. De Bary gives an account of his 

 interpretation of the word spore. Though known in a 

 general way respectively as zoospores and spores the asexual 

 reproductive cells of algae are termed gonidia (Gr. gone, 

 offspring), and of fungi, conidia (Gr. konis, dust). The 

 term swarm-spore is sometimes used as equivalent to zoo- 

 spore. The fertilised ovum, as in Vaucheria, is called an 



