324 Haemogregarines 
In most cases it is altogether'ignored, or the author barely mentions that 
the parasite is enclosed in a capsule, without any further definition or descrip¬ 
tion. 
With regard to the nature of this structure the opinions of authors differ. 
Some (Langmann, 1899; Laveran and Pettit, 1911) regard the light area 
surrounding the parasite as an artificial product, due to unequal contraction 
of the protoplasm of the parasite and host cell under the action of fixing 
agents, resulting in detachment of the parasite from the cytoplasm of the 
erythrocyte; hence the empty space which is absent in normal ones. 
The majority of authors (Prowazek, 1907; Dutton, Todd and Tobey, 1907; 
Dobell, 1908; Sambon, 1908; Robertson, 1908, 1910; Seidelin, 1911; Stevenson, 
1911; Conor, 1912; Reichenow, 1912; Schubotz, 1913; Sergent, 1918, and 
others), however, state definitely that the parasite is surrounded by a special 
membrane or capsule. Sambon (1908) says: 
“The examination of numerous species of haemogregarines...has convinced 
me that all the endocorpuscular forms, save the very earliest, are enclosed 
within a shell or capsule produced by the parasite itself, either by means of 
a special secretion or by a process of ecdysis, the haemogregarine shrinking 
from its detached former skin, as do certain flies in the formation of their 
puparium. The capsule varies much in size, shape, thickness, transparency 
and other particulars according to the species of haemogregarine to which it 
belongs, as well as to the stage of development....The presence of a capsule 
may be evidenced by a number of indications. Thus, in preparing films for 
microscopical examination, some of the haemogregarine-infested blood cells 
may be disrupted; the parasites remain closely doubled up, being evidently 
confined by a capsule, to the exterior of which fragments of the host cell 
nucleus may be seen adhering....Sometimes we may detect a second inner 
shell produced by a subsequent ecdysis. This inner membrane may also show 
deeply staining granules. After the escape of the parasite the remains of the 
broken capsule may be seen either still within the host cell or free in the liquor 
sanguinis....The capsule appears to burst along definite lines of cleavage.... 
Two of these lines are to be seen, one at each end of the capsule....After 
bursting open the two halves of the capsule roll up after the fashion of the 
mature seed pods of certain leguminous plants/’ 
Similar statements are made by other authors. Thus, Prowazek also found 
“urn den in einer Hohlung der Zelle ruhenden Parasiten...eine rotfarbbare 
Niederschlagsmembran.” Dutton, Todd and Tobey encountered in the blood 
of snakes and amphibia curled remains of the capsules in the form of “rods” 
lying in pairs. According to Dobell, Robertson and Sergent the capsule is not 
only distinctly visible in intracorpuscular forms, but may frequently be en¬ 
countered either free in the plasma, or in the corpuscles abandoned by the 
parasites. Seidelin also observed delicate red lines at the extremities of the 
capsule (Sambon’s “lines of cleavage”), and Stevenson stated that the “cyst 
wall” was double at the end at which the parasite is bent, the space between 
