552 



BIOLOGY OF THE PROTOZOA 



processes of the capsule are regarded by Doflein as supports in 

 floating, evidence for which is given by Kofoid's observation of 

 these spores in plankton. 



Fig. 221. — Spores of Actinomyxida. ^4, Hexaetinomyxon psammoryctis, after 

 Stole.; B, Sphaeractinomyxon stolgi; C, Triactinomyxon ignotum; D, same, spore-bearing 

 part enlarged, after Leger; E, Synactinomyxon tubificis. (After Caullery and Mesnil.) 



Order 3. Microsporidia Balbiani. 



Probably because of their minute size the organisms included in 

 this Order are incompletely known and many points of structure 

 and of life history are still unknown or controversial. They are 

 practically all cell parasites which enter the host by way of the 

 digestive tract from which they may spread to all tissues of the 

 body, causing epidemics not only in fish but, economically more 

 important, costly epidemics in silkworms (Nosema bombyces Naeg.) 

 and honey bees (Nosema apis Zander). Pseudopodia and ameboid 

 movement are rarely observed (Nosema marionis Thel). Inter- 

 mediate hosts are unknown. 



Agamous reproduction is well established through the observa- 

 tions of many investigators. The agametes are small, uninucleate, 

 and usually with indefinite outlines which scarcely delimit them 

 from the host cell protoplasm; they may have one or several nuclei, 

 and multiply actively by simple division resulting frequently in 

 chain formation through successive nuclear divisions and delayed 

 cell division (Fig. 222). As a result of such agamous reproduction 

 all of the tissues of the host may become infected and myriads of 



