150
MARINE MOLLUSCS AS HOSTS FOR SYMBIOSES
endogenous budding (Sprague, 1954) resulting in numerous minute
gametes. The gametes resulting from one gametocyte are smaller and
C Y C LE
t
A = = = = = d R
\N
M U D C R A B
C Y C L E
O Y S T E R
"
.I
PIG. 30. Stages in the life cycle of Nematopsis ostrearum. A, Spore in oyster containing
a sporozoite ; B, sporozoite escaping from spore in intestine of crab ; C, attachment
to host's intestinal epithelium ; D, development into trophozoite or sporadin ;
E, coupling of sporadins; F, temporary reattachment to intestinal wall ; G, mature
sporont ; H-J, sporonts in syzygy followed by attachment to crab's rectum and
formation of gametocyst ; K, sporozoites escaping from ruptured gametocyst ;
L, single gymnospore; M, engulfment of gymnospore by host's phagocyte and
breaking apart of sporozoites ; N-Q, growth of sporozoites within phagocyte and
formation of resistant spores. (Redrawn after Prytherch, 1940.)