CRUSTACEAN BLOOD COAGULATION. 193 



Deeapoda, and it is of especial interest to know if coagulation C occurs 

 among them. Of this order I liave examined Fandalns montagui and 

 P. brcvirostfis, Hippolyte varians and H, viridis, Palacmon serratus, 

 Crangoii vulgaris, Palinurus vulgaris, Homarus vulgaris, Astacus 

 Jluviatilis, Galathca squamifera and G. strigosa, Porcellana longicornis 

 and P. platgchelcs, Eupagurus hcrnhardus and E. prideauxii, Ehalia 

 tuberosa, Corystes cassivelaunus, Carcinus macnas, Portunus puber, P. 

 mar mo reus, P. arcuatus and P. depurator, Atelecyclus scptemdentatus, 

 Cancer pagurus, Xantho hydrophilus and X. incisus, InacJms dorynchus, 

 Macropodia rostratus, Hyas coardatus and Maia squinado ; and have 

 found coagulation C only in two members of the list, viz. in Palinurus 

 and in Astacus. It is thus an uncommon form of coagulation in the 

 Deeapoda, while it is doubtful if it occurs at all in the Brachyura. 



The examples hitherto mentioned exhaust the crustacean forms 

 in which I have looked for the presence of coagulation C. I shall now 

 say a word or two regarding this form of coagulation in its physio- 

 logical aspect. 



The clotting associated with the presence of explosive cells is a 

 sufficiently striking one. Thus the blood of Palinurus forms the 

 stillest jelly of any crustacean blood I have examined; Ligia blood 

 also forms a specially firm coagulum ; while the onset of coagulation is 

 in all cases rapid. In the solidity of the jelly formed, coagulation C 

 represents the most advanced form of coagulation to be met with 

 in Crustacea. 



Assuming that the object of plasma coagulation is to provide an 

 additional mechanism for stopping a wound (cell-agglutination being, 

 as above indicated, the primary and most essential mechanism for this 

 purpose) it would follow that, ceteris paribus, a haemorrhage in an 

 animal possessing explosive cells would cease sooner than a hae- 

 morrhage in other Crustacea. This being so, one would look in isopods, 

 in Palinurus and in Astacus for some special cause necessitating 

 the existence of an extraordinary mechanism for arrest of haemorrhage. 



One naturally thinks of the process of autotomy in this connection. 

 The reflex surrender of damaged limbs is generally conceded to be a 

 method of preventing undue loss of blood. Where the reflex is 

 present in least degree one might expect on the whole to find the 

 highest degree of coagulability of the blood, and vice versa. 



Now isopods do not show autotomy. In Astacus the reflex is said 

 to be present — Huxley (80) — though in my own experience and in 

 that of others, e.g. Fredericq (83), it is not readily demonstrable even 

 in specimens presumably fit and healthy. In isopods and in Astacus, 

 tlierefore, the association is wliat one would a priori expect. In 



