384. ALDO CASTELLANI AND ARTHUR WILLBEY. 
phases, leaves abundant room for future discoveries of 
biological importance.! 
Schaudinn’s memorable discovery, that the well-known 
heematozoon of birds called Halteridium is a phase in the 
life-history of species of Trypanosoma, has considerably 
modified the views as to the generic autonomy of the various 
protozoon parasites of the blood, besides apparently demon- 
strating a close affinity between the Sporozoa and the 
Flagellata. The name Halteridium will, however, doubt- 
less survive to characterise the particular phase referred to, 
and the samé use may probably be made of the term Hemo- 
cystidium, which we have introduced to denote a well- 
marked endoglobular parasite observed by us in a gecko, 
an analogous phase having been previously described by 
Dr. Simond from a Trionyx. 
I. On some Free, UNPIGMENTED GREGARINIFORM BopiEs 
OBSERVED IN THE Bioop or MAN ann Birps. 
In the course of our examination of numerous samples of 
blood collected in different parts of the island, very many 
negative results, as was to be anticipated, have been obtained. 
So far as our observations have extended, they seem to 
point to the conclusion that the percentage of infected cases 
of all kinds is greater in the neighbourhood of centres 
of population than in outlying districts. This fact may 
indicate that the conditions of nutrition of the Heematozoa 
are more suitable under the circumstances of sanitation 
peculiar to towns, and that the incidence of blood-parasitism 
may be directly or indirectly assignable to the far-reaching 
influences of domestication. 
There seems to be a marked contrast between the distribu- 
tion of the Heematozoa and that of the majority of Entozoa 
or parasites of the digestive tract, the latter being at least 
1 There is, however, a paper by Dr. Siegel on “ Die geschlechtliche Entwick- 
lung von Hemogregarina stepanovi im Riisselegel, Placobdella 
catenigera,” ‘ Arch. Protist,’ vol. ii, 1908, pp. 339-342. 
