4 SMITHSONIAN MISCELLANEOUS COLLECTIONS VOL. 134 
fluid hemolymph reached a standstill before alterations started in the 
fragile hyaline hemocytes. The successive steps of the coagulation were 
observed by phase-contrast microscopy (Wild M/1o). Whenever 
possible, several samples were collected from each specimen. In view 
of the rapid completion of the process (within a few seconds in many 
insects), desiccation did not interfere with the observations, and the 
edges of the preparations were not sealed. When the reactions failed 
to appear (see pattern IV, below), the preparations were stored in 
petri dishes under high moisture and examined subsequently at differ- 
ent times. Some degree of evaporation and moderate condensation 
of the plasma along the edges of the films were incidentally detected in 
those preparations kept for several hours in moistened petri dishes. 
RESULTS 
DESCRIPTION OF THE PATTERNS OF COAGULATION 
The classification of coagulation of insect hemolymph into four 
tentative patterns, used in the present study, is essentially based on 
differences in the following processes: 
1. The irreversible alterations affecting a category of hyaline hemo- 
cytes, highly sensitive to contact with solid surfaces, and playing a 
selective part in the inception of the coagulation, in contrast with the 
other blood corpuscles. In the conditions of phase-contrast micro- 
scopy, the unstable hyaline hemocytes appear, especially after their 
alterations, as pale, round vesicular elements. Their nucleus is 
sharply outlined, relatively small. A few dark granules are scat- 
tered in the hyaline cytoplasm. In the other categories of hemocytes 
(small stem cells, transitional forms, and various kinds of granular 
hemocytes) the nucleus is distinctly larger and the cytoplasm darker. 
The cytological differences between the fragile hemocytes and the 
other kinds of blood cells have been illustrated in previous papers 
(Grégoire and Florkin, 1950; Grégoire, 1951, 1953, 1955a), and ap- 
pear in figures I, 2, 8, and 9 of plate 1. 
2. The modifications of the plasma, following or accompanying the 
alterations in the fragile hyaline hemocytes. 
Text figures 1-4 illustrate schematically the microscopical charac- 
ters of the four patterns. 
Pattern I. Inception of the plasma coagulation in the shape of ts- 
lands of coagulation around the hyaline hemocytes (text fig. 1; pl. 1, 
figs. I, 2, 3, 4, 5, and 7).—Selective alterations in the unstable hyaline 
hemocytes result in exudation or in explosive discharge of cell ma- 
terial into the surrounding fluid. Coagulation of the plasma starts in 
