272 GENERAL ANATOMY OR HISTOLOGY OE BLOWFLY. 



of blood corpuscles is Schiifer's.* The blood is spread in a thin 

 layer on the cover-glass, and fixed by holding it in the steam of 

 boiling water, or passing the cover rapidly through the flame of 

 a spirit-lamp. In this way the corpuscles may be fixed in the 

 amoeboid condition. The preparation is then stained by 

 putting a drop of Ehrlich's hsematoxylon on it for a few 

 seconds. It is then washed rapidly with distilled water, and 

 placed in hard water until the stain becomes blue, after which 

 it is mounted in balsam in the usual way. 



Some of these preparations are very beautiful, and exhibit 

 both the intracellular reticulum, spongioplasm, and the intra- 

 nuclear network, chromatin fibres. The appearances are pre- 

 cisely similar to those seen by Schiiferf in the white corpuscles 

 of the newt. As in the newt, they frequently exhibit pyriform 

 nuclei drawn out into long tails. 



When the fresh blood of the larva is treated with a solution 

 of magenta, the corpuscles swell up and discharge a granular 

 mass, which leaves a perfectly transparent stroma around the 

 nucleus (Fig. 17, 2, g h i). 



H. Landoist and others have described crystals in the 

 blood of Insects. Whenever I have observed crystals, I have 

 always been able to trace them to some reagent used in the 

 preparation. Staining with lithia carmine invariably gives 

 rise to crystals of lithia salts. The same author states cor- 

 rectly that the blood plasma contains a globulin which is 

 precipitated by COo, or acetic acid and other reagents. He 

 also remarks that magenta produces the appearance known as 

 ' Robert's macula.' Viallanes devotes a chapter to the con- 

 sideration of the state of the blood of the larva immediately 

 before its metamorphosis [27, pp. 131-136], which he sum- 

 marises in the following manner : ' The cells of the blood of 

 the larva are analogous to the leucocytes of Vertebrates, and 

 are typical embryonic cells.' 



* Schiifer, E. A., ' On the Structure of Amoeboid Protoplasm,' Proc. Roy. 

 Soc.,vol. xiix., 1891. 



t Ibid. 



X Landois, H., ' Krystallisation in Insectenblut,' Zeitsch. f. w. Zool., 

 Ba. xiv. 



