124 



The Blood. 



The blood is an almost transparent fluid having a 

 slight pinkish-blue tint (due to the presence of haemo- 

 cyanin). The colour deepens on exposure to air. The 

 blood consists of an almost colourless lymph in which are 

 found numerous small cells or amoebocytes. There are two 

 principal kinds of amoebocytes: — (1) Semi-transparent 

 cells, which are amoeboid and have finely granular proto- 

 plasm. There is a well-defined nucleus. (2) Globular 

 cells containing refringent granules. As pointed out by 

 Cuenot,* these granules are similar to the eosinophilous 

 granules recognised by Ehrlich in the leucocytes of 

 various vertebrates. Hence Cuenot designates the second 

 kind the Eosinophilous amoebocytes.^ They are composed 

 of an albuminous material. 



In the neighbourhood of the cephalic artery, above 

 the fore-gut, is a cellular mass which, according to 

 Cuenot, is a lymphatic gland in which the amoebocytes 

 are formed. 



Cuenot has recognised five kinds of amoebocytes in 

 the blood, which are all stages in the transformation of 

 the clear amoebocytes mentioned above. The eosino- 

 philous amoebocytes are also formed from the clear 

 amoebocytes, and mark a stage in the degeneration of the 

 cell. The eosinophilous granules present in the amoebo- 

 cyte are small and few in number at first. They become 

 comparatively large in size and very numerous until the 

 entire cell is filled with a solid mass. The cell then 

 degenerates rapidly and finally disappears. The granules 



* Cuenot, L. " Etudes physiologiques sur les Crustaces Deca- 

 pod es." Archives de Biologie, T. XIII, 1895, p. 245. 



t The granules readily take the following stains :— Picric acid, 

 eosin, indigo-carmine, fuchsine acid and " orange G." They remain 

 absolutely colourless under the following stains : — Methyl green, 

 dahlia, crystal violet, methylene blue and safranin. (Cuenot). 



