LIFE-HISTORY OF THE PARASITES OF MALARIA 185 
species (genus Haemamoeba) the gametocyte has a general form similar to that of the 
sporocyte before the spores are produced ; but in one species (genus Haemomenas) 
the gametocyte has a special (crescentic) shape, which is recognisable at an early 
stage in its career. As their name indicates, the gametocytes are sexual forms, male 
and female. They possess no function within the vertebrate host, but are meant to 
continue the lite of the organisms within a second host — a suctorial insect. 
When the gametoyctes are drawn into the stomach cavity of gnats (middle 
intestine) they immediately undertake their sexual functions. The male gametocyte 
(the nucleus of which is larger than that of the female) is destined to give origin to 
a number of microgametes, or spermatoza ; the female gametocyte develops into one 
macrogamete, or ovum, together with a residuum consisting chiefly of melanin. 
A few minutes after ingestion by the gnat both male and female gametocytes break 
from the enclosing corpuscle, and swell slightly. Attached to the naked parasite one 
can now often perceive one or two small spherical objects, which may possibly be the 
homologues of polar bodies. A few minutes later a quivering movement is observed 
in the male gametocytes, due to the emission of the microgametes. These bodies are 
long filaments endowed with very active powers of locomotion, and consisting of a 
thread of chromatin surrounded by a thin scroll of bioplasm. Breaking away from 
the parent cell, and leaving behind the melanin of that cell as a residuum, the micro- 
gametes travel through the liquor sanguinis contained in the stomach of the gnat in 
search of a macrogamete. This being found, one microgamete enters the macrogamete 
and unites with its nucleus, producing a zygote. 
Shortly after the act of fertilisation the zygote may in some species become 
motile (when it is technically called a vermicule), and generally changes its shape. 
At all events, it travels towards the parietes of the stomach. If the insect be of an 
inhospitable species the zygote perishes ; but if the insect be hospitable the zygote 
passes through the parietes and affixes itself on or just under the outer muscular coat 
of the stomach. Here it becomes motionless and commences to grow rapidly in size. 
At first of about the size of a red corpuscle, and still containing the characteristic 
black granules of melanin, the zygote, after a week or so, reaches a very large size ; that 
is, it becomes about 60 /j. in diameter, or about eight times its original diameter, and 
about five hundred times its original bulk. As we have said, we are not satisfied regard- 
ing the nature of the nuclear changes during the growth of the zygotes, but it is clear 
that the parasite acquires a very distinct capsule, and that its substance divides into from 
eight to twelve meres, which can easily be distinguished without staining. Each mere 
seems finally to become a spherical blastophore, bearing on its surface a number of 
filamentous, or rather spindle-shaped blasts, in the manner depicted in Fig. 60 ; at 
least, it is easy, by rupturing a nearly mature zygote, to expel a number of such bodies. 
When the zygote reaches maturity the blastophores disappear, leaving the capsule 
packed with thousands of the blasts (and containing also some residual fatty globules). 
