622 W. S. PERRIN. 
possess a spore-coat or shell which is highly resistent to the 
action of reagents. The spores gain the exterior in the feces 
of the cockroach. Doflein calls the production of naked 
swarm spores for auto-infection, and resting coated spores for 
infection of fresh hosts “ multiplicative” and “ propagative” 
methods of reproduction respectively. Among the Myxo- 
sporidia it is usual as a preliminary to sporulation for the 
trophozoite to produce a number of internal buds, which give 
rise to a varying number of spores, the production of spores 
continuing within the trophozoite without any cessation of 
its activity or growth. ‘These internal buds haye been styled 
by Gurley pansporoblasts. In Pleistophora periplanete, 
however, no such formation of pansporoblasts occurs, the 
whole of the trophozoite simply withdrawing its pseudopodia, 
rounding itself off and producing spores. As, however, the 
classification of the Myxosporidia is largely based on the 
features exhibited by the pansporoblast, the number of spores 
it produces, etc., it seems advisable to regard the trophozoite 
of Pleistophora periplanete as producing one pansporo- 
blast, although the point at which trophozoite ceases to be 
trophozoite and becomes pansporoblast may not be easy to 
define. 
As a matter of fact I am inclined to regard the production 
of the deeply staining purple nuclei (figs. 9,10, 12) as indica- 
tive of incipient sporulation for the following reasons : 
(1) As mentioned above these nuclei never occur in tropho- 
zoites, which may be inferred to be actively metabolic, e. g. 
trophozoites in any of the stages of multiplicative repro- 
duction. 
(2) he presence of these nuclei is associated with an 
absence of pseudopodia and a general appearance, as though 
the trophozoite were rounding itself off to form a pansporo- 
blast (tigs. 9, 10). 
(3) Apart from the spores it produces, the pansporoblast 
contains a considerable amount of protoplasm and a number of 
nuclei, which are not used in the production of spores. hese 
nuclei are left behind, and, during the later stages of sporu- 
