176 



THE MORPHOLOGY OF THE COMMON CRAYFISH. 



of the Doay consists of one or more of the following eight 

 histological grouj^s : — 



1. Blood corpuscles ; 2. Epithelium ; 3. Connective 

 tissue; 4. Muscle ; 5. Nerve; G. Ova; 7. Spermatozoa; 

 8. Cuticle. 



1. A droi3 of freshly-drawn hlood of the crayfish con- 

 tains multitudes of small particles, the hlood corpuscles, 









JO 



Fig. 49. — Antacvs fliiviafilin. — The corpuscles of the blood, highly 

 magnified. 1 — S, show the changes undergone by a single cor- 

 puscle during a quarter of an hour ; ?i, the nucleus ; 9 and 10 

 are corpuscles killed by magenta, and having the nucleus deeply 

 stained by the colouring matter. 



which rarel}^ exceed l-700th, and usually are ahout 

 1-lOOOth, of an inch in diameter (fig. 49). They 

 are sometimes pale and delicate, but generally more or 

 less dark, from containing a number of minute strongly 

 refracting granules, and tlie}^ are ordinarih^ exceedingly 

 irregular in form. If one of them is watched continu- 



