160 PROTISTS AND DISEASE 



mycetozoan nucleus than is that of Synchytrium when in 

 mitosis, the former having 10 or 12 chromosomes, the latter 

 in the asexual sorus of 8. endobioticum, only 5. 



The conjugation of similar zoospores to form the myce- 

 tozoan plasmodium is an algal trait, which is found also in 

 some monads. We may compare the growth of the synchy- 

 trian zygote with that of the plasmodium of a parasitic 

 form more justly perhaps than with free-living myceto- 

 zoa. The synchytrian grows by chromidial or plasson 

 extensions from a nucleolus to form what is really a plas- 

 modium limited in extent by a cell- wall. Plasmodiophorans 

 grow by nuclear divisions, the chromidial phase being 

 assumed as a brief stage after growth is complete. Zygote 

 formation has not as yet been seen in them. 



The Animalia monadida fall into two groups, Acra- 

 spedina and Craspedina, according as the flagellum has 

 not, or has, a collar (Gr. kraspedon) round its base. The 

 Monadida Acraspedina include free-living forms such as the 

 Rhizomastigina, of which a phase of one species, Mastigella 

 vitrea, has been mentioned in Chapter I ; together with 

 many parasites, such as, of blood-parasites, the genus 

 Trypanosoma (see Part I), causes of sleeping-sickness, &c. ; 

 tissue-parasites, such as Leishmannia donovani, the cause of 

 black-fever and splenomegaly (see Part II) ; and innumer- 

 able intestinal parasites such as Copromonas subtilis of the 

 frog. 



Two monads described by Cienkowsky, M. parasitica 



