No. 6 HEMOLYMPH COAGULATION IN INSECTS—GREGOIRE 29 
scopical picture of films of clotting hemolymph, observed by phase- 
contrast microscopy in standard conditions of preparation. 
Objection that these patterns might result from random artifacts 
has been examined elsewhere (Grégoire, 1955a). 
In control observations, the clotting process was compared in films 
of hemolymph spread out under glass by the standard procedure and 
in clot plugs spontaneously formed at the wound site and gently 
squeezed under glass after completion of the process. In both in- 
stances, the microscopical alterations characterizing the same pattern 
were recorded. The standard conditions of preparation of the samples 
of hemolymph seem therefore to be a faithful reproduction of the 
alterations occurring during the undisturbed natural process. 
2. Whatever each pattern might signify at the cytological ? or bio- 
chemical level,* most results of the present and other studies * suggest 
2 Among the factors implied in the process of coagulation, the patterns reflect 
actual inequalities between species and higher taxonomic groups in the degree 
of sensitiveness to contact with solid surfaces of the fragile hyaline hemocytes 
selectively involved in the inception of the coagulation, in the nature of the 
alterations undergone by these unstable cells, and in the rapidity with which 
these alterations develop. These differences affect the subsequent reaction of 
the plasma. As shown in the present and in previous studies, a similar degree 
in sensitiveness of the fragile hemocytes is frequently shared by insects belong- 
ing to a same group. 
A tentative identification of the fragile hyaline hemocytes has been reported 
elsewhere (Grégoire, 1953a; 1955a, p. 129). A part of these corpuscles exhibits 
cytological features in common with the oenocytoids. In several groups (Odo- 
nata, Hemiptera-Heteroptera, various species of Coleoptera, lepidopteran and 
dipteran larvae, Trichoptera, and some Hymenoptera) these corpuscles appeared 
in the films of hemolymph in the shape of highly refractive or dark hyaline 
hemocytes, which undergo clarification after explosive discharge of substance. 
The same corpuscles differ, however, in other characters from the classical 
description of the oenocytoids (1955a, discussion, p. 131). On the other hand, the 
fragile hemocytes selectively involved in coagulation are referred to by Jones 
(1954) as cystocytes, in Tenebrio molitor. 
3 The scarcity of the data available at the present time does not enable one 
to establish whether actual biochemical differences characterize each of the 
four patterns, and especially the two aspects presented by the reactions in the 
plasma, the granular substance (in the islands of coagulation and in the areas 
of extension: pattern I), and transparent glassy veils (pattern II). As sug- 
gested by observations of films of varying thickness, it is unlikely, as reported 
elsewhere (Grégoire, 1955a, discussion, p. 128) that the twofold aspect of the 
plasma changes is related merely to differences in concentration or in thickness of 
the clotted films. The veils are not to be identified with the products of general 
disintegration of the hemocytes (cell fibrin). 
An adequate test of the validity of the patterns would be to determine 
whether biochemical differences correspond to microscopical pictures as dif- 
ferent as those consistently recorded, for instance, in insects belonging to the 
