Details of what occurs in the interval between the hatching of amœbulæ from the spores of the Proteus group of amœbæ to the attainment of the adult condition (4–6 months) not hitherto known are described. The method consists in removing mature adults to petri dishes 4 in. in diameter, containing a dilute inorganic fluid which causes sporulation. The subsequent development of the hatching amœbulaæ can be traced in situ by means of a 4·4 mm. water immersion lens, and is seen to consist of feeding and growth alternating with periods of encystment. The time spent in cysts greatly exceeds that of activity.
Some account of what takes place when cultures of the Proteus group, allowed to dry to a brownish dust, and then wetted, is given. Only in the case of A. proteus have the amœbulæ, which hatch out from the spores, been grown to maturity. It has been shown that the dried cultures used may comprise (1) spores, (2) cysts of varying size from which arise amœbulæ likewise varying in size.