98 



PROTOZOA 



1. Myxosporidiaceae. — Naked parasites in cold -blooded animals. Spore- 

 formation due to an aggi'egation of cytoplasm around a single nucleus 

 to form an archespore, which then produces a complex of cells ■\\'ithin 

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

 ]\Ty:i:idium'Bntsch.; Myxohohis Butsch. ; Henneguya Thelohna ; Nosema 

 Nageli ( = Olugea Th.). 



2. AcTiNOMYXiDiACEAE.i — 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 double membrane ; spores simple. Sarcocystis Lankester. 



Monoeystis offers us the simplest type of Gregarinidaceae. In 



most Gregarines (Figs. 31,32) the sporozoite enters the epithelium- 



tletb 



opd 



FiG. 32. — Gregarina hlaltarum Sieb. A, two cephaloiits, enibetWed by their epimerite 

 {ep), ill cells of the gut-epithelium ; deiL, rleutonierite ; nu, nucleus ; pr, protomerite ; 

 B^, B-, two free specimens of au allied genus ; the epimerite is falling off in B"^, 

 which is on its way to become a sporout ; C, cyst (cy) of A, with sporoduots {spd) 

 discharging the spores [sp), surrounded by an external gelatinous investment (g). 

 (From l^arker and Haswell.) 



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

 protrudes the greater part of its bulk 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 (" deutomerite "), 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 Caullery and Mesnil, "Rech. sur les Actinomyxidies," Arch. Bot. vi. 1905, 

 p. 272 f. . 



