ZOOLOGY AND BOTANY, MICROSCOPY, ETC. 
609 
Malaria Parasites.* — Dr. R. Ross, in a short account of the life* 
history of the parasites of malaria, points out that the youngest parasites 
exist as amoebulae or myxopods within red corpuscles. In the course of 
a few days they become either sporocytes or gametocytes. The sporo- 
cytes are produced asexually, and contain spores which on maturation 
break through the red corpuscle and become disseminated in the 
plasma ; each sporelet attaches itself to another corpuscle, and so on. 
The gametocyte may resemble a sporocyte in appearance, or be crescent- 
shaped. Further development is only attained in an intermediate host, 
and this is reached in the alimentary canal of certain suctorial insects, 
where they become endowed with sexual functions. The male gameto- 
cytes emit a variable number of microgametes, which seek the female 
gametocytes. These are motionless macrogamotes. From the union of 
the two is produced a zygote, a round or oval cell 8-10 fx in diameter. 
In the body of the insect host the zygotes grow and undergo certain 
changes, becoming zygotomeres, then blastophores, and finally zygoto- 
blasts. The latter are discharged into the insect’s blood, and are then 
seen to be delicate flagellulae or mastigopods, 12-16 fx in length. FiVen- 
tually the mastigopods reach the salivary glands, where they accumulate 
in large numbers. During haustcllation they escape from the gland, pas- 
sing along the duct into the blood of a new vertebrate host. Apparently 
therefore the mastigopod is the ainosbula or myxopod. Until the zygo- 
toblast stage the various forms contain pigment-granules derived from 
the haemoglobin of the red corpuscles. 
For classification purposes, the author divides the family Haemamoc- 
bidae into two genera, one having four species, i.e. Hsemamoeba, the other, 
Hsemomenas , only one. 
In Hdemamceba the mature gametocytes are similar in form to tLe 
mature sporocytes before the spores have been differentiated. In Hsemo- 
menas the gametocytes have a special crescent form. 
The most common intermediary host is found to be Anopheles cla- 
viger. 
Development of Malaria Parasites, j — The report of Prof. R. Koch, 
Prof. Kossel, and Prof. Pfeiffer, while containing little new except what 
relates to the vermiform stage, is useful, as it confirms and elaboiates the 
work of others with regard to the life-history of the malaria parasites 
Halteridium and Proteosoma. The following is a summary of their de- 
velopment (1) Young parasite composed of chromatin nucleus and 
very scanty plasma ; no nucleus. Lives in or on red corpuscles. (2) 
Adult composed of chromatin, pigment, and with relatively much in- 
creased plasma. From this point development may proceed in two ways. 
(3) Endogenous , i. e. in the body of the principal host. Simple division 
into numerous small particles which commence their cycle afresh, aban- 
doning the pigment in the mother-cell. (4) Exogenous, i.e. in the body 
of the intermediate host (mosquito). Parasite leaves the blood-corpuscle, 
and can be differentiated into male and female. (5) Formation of 
spermatozoa and impregnation of female. (6) Conversion into vermi- 
form bodies which (7) pass through the stomach walls and form coccidia- 
* Nature, lx. (1899) pp. 322-4, 439. 
f Zeitschr. f. Hygiene u. Infekt., xxxii. (1899). See Blit. Med. Journ., 1899, ii. 
p. 1039. 
