62 



PROTOZOA. 



bodies which are naked and do not further sub-divide. These constitute the 

 young form, and may be compared to the spores of the other forms. They are 

 set free in the blood on the breaking down of the cell-host, and soon enter 

 another corpuscle, where they acquire their full size. They then leave the 

 corpuscle and enter upon the stage described above, during which they live freely 

 in the blood. They have been observed to conjugate completely in pairs in this 

 free stage. In the free state they move either by serpentine bending of the body 

 or by wave-like contractions of the body substance. It is not known how they 

 are transported to a new host. 



Drepanidium Lankester, Rana, Aves ; Karyolysus Labbe, Lacerta ; Dani- 

 lewskya Labbe, Lacerta, Cistudo, Rana. 



d 



FIG. 48. a-c, red blood-corpuscles of the frog infected with Drepanidium prince ps ; d, free 

 forms in movement (from Wasielewski after Labbe). 



Sub-order 2. ACYSTOSPORIDIA.* 



These are amoeboid cell-parasites, found only in vertebrata (except fishes and 

 reptiles). They do not form a cyst-wall. They mainly infest red blood- 

 corpuscles, but are also sometimes found in the kidney, liver, and intestinal 

 epithelium. They cause hypertrophy of the corpuscle and a diminution of its 

 haemoglobin. 



The Acystosporidia are specially interesting, because they include forms 

 which are associated with some important diseases in certain of the larger 

 mammals, e.g., malaria in man and Texas-fever in cattle. They are minute 

 amceboid organisms, with a nucleus and pigment-grains (Fig. 49). They never 

 leave their cell-host, and their movements, which are always amoeboid, take 

 place within the cell. They readily undergo degenerative changes in prepara- 

 tions of the blood of infected animals. These changes consist in the disruption 

 of their corpuscular host and in the thrusting out of vibratile processes, which 

 break off from the body (Fig. 50) : this is the so-called Poly 'mi 'his- form. 

 Finally the body itself breaks up. 



They reproduce in their cell-host by the formation of minute spores without 

 encystment. They first assume a rounded form ; the nucleus then breaks up 

 (so-called one-spored forms) into a number of minute fragments, around which 

 a portion of the protoplasm becomes segregated (Fig. 51) ; these small nucleated 

 fragments constitute the naked spores of the animals. In some cases the 

 nucleus divides (so-called two-spored forms) into two before breaking up, so 



* A. Labbe, "Parasites eudoglobulaires. " Arch. Zool. cxper. (3), 2. Laveran, 

 L'Hematozoaircdupaludisiitc, Paris, 1891. J. Manuaberg, Die Malariaparasiten, 

 Vienna, 1893. 



