98 



PROTOZOA 



1. ^Iyxosporidiaceae. — Naked parasites in cold-blooded animals. Spore- 

 formation due to an aggregation of cytoplasm around a single nucleus 

 to form an arcliespore, which then j^roduces a complex of cells within 

 which two daughter-cells form the spores and accessory nematocysts. 

 Mijxidium Biitsch. ; Myxoholus Blitsch. ; Henneguya Thelohan ; Nosema 

 Nageli {=Glu(jea Th.j. 



2. AcTiNOMYXiDiACEAE.^ — Apocyte resolved into a sporange, containing 

 eight secondary sporanges (so-called spores), of ternary symmetry and 

 provided with three polar nematocysts. 



3. Sarcosporidiaceae. — Encysted parasites in the muscles of Vertebrates, 

 with a doulile membrane ; spores simple. Sarcocystis Lankester. 



Monocystis offers us the simplest type of Gregarinidaceae. In 

 most Gregarines (Figs. 3 1,3 2) the sporozoite enters the epithelium- 



Fig. 32. — Gregarina hlaiiarum Sieb. A, two eeplialoiits, embeilded by their epimerite 

 [cp), ill cells of the gut-epithelium ; den, deutonierite ; nn, nucleus ; pj\ protonierite ; 

 B\ B'-, two free specimens of an allied genus ; the epimerite is falling off in B", 

 which is on its way to become a sporont ; C, cyst {cy) of A, with sporoducts (s^rZ) 

 discharging the sjjores {sp), surrounded by an external gelatinous investment (</). 

 (From Parker and Haswell.) 



cell of the gut of an Arthropod, Worm or Mollusc, and as it enlarges 

 protrudes the greater part of its Inilk into the lumen, and may 

 become free therein, or pass into the coelom. The attached part 

 is often enlarged into a sort of grapple armed with spines, the 

 " epimerite " ; this contains only sarcocyte, the other layers being 

 absent. The freely projecting body is usually divided by an 

 ingrowth of the myocyte into a front segment (" protomerite "), 

 and a rear one (" deutonierite "), with the nucleus usually in the 

 latter. In this state the cell is termed a " cephalont." Con- 

 jugation is frequent, but apparently is not always connected with 



^ See CaulJery and Mcsnil, "Rech. sur Ics Actinomyxidies," Arch. Bot. vi. 1905, 

 p. 272 f. 



