258 Reaction of certain Cell-Granules with Methylene- Blue. [Nov. 9, 



granules surrounding the lumen and extending about half-way 

 towards the basement membrane, while outside this there was a 

 zone of blue-staining granules. This suggests that the rose-stain- 

 ing condition is a final stage in the elaboration of the constituents 

 of the granules of these cells. 



A still more instructive example is found in the ectoderm cells 

 of the Ammoccete larva which I examined at the request of Dr 

 Gaskell. These cells are each overlaid by a thick cuticle per- 

 forated by coarse canaliculi which lead from the cell protoplasm to 

 the external surface of the animal. Miss Alcock has shewn that 

 these cells, under appropriate stimuli, discharge on to the general 

 surface a viscid substance which has the power of rapidly digesting 

 fibrin in an acid medium. If these cells are treated with methy- 

 lene-blue we find (1) that the extruded secretion gives the rose 

 reaction, (2) that the pores in the cuticle may appear as rose- 

 coloured rods, owing to their being filled with the secretion, and 

 (3) that the cells themselves are occupied by rose-coloured granules 

 which lie in the half of the cell next to the cuticular border, and 

 by blue-coloured granules which occupy their deeper portions. 



In the ectoderm of Daphnia rose-coloured granules are scanty, 

 while, under certain circumstances to be detailed elsewhere, the 

 cells may include a number of large vacuoles, the contents of 

 which give a brilliant rose reaction. In connection with the 

 presence of these vacuoles we find that Daphnia possesses the 

 power of extruding on to its surface, through cuticular pores, a 

 substance which swells up to form a jelly in water, and stains 

 brilliant rose. This particular case will receive more detailed 

 description on some future occasion. For the present I will only 

 say that the secretion is used by the animal to prevent parasitic 

 vegetable or animal growths obtaining a foothold on the shell. 



I have never yet found a blood or lymph cell with both blue 

 and rose-staining granules. It may be regarded as probable that 

 blue-staining granules are absent from wandering cells. The cells 

 with rose-staining granules have a remarkable distribution. In 

 Astacus, as I have noted elsewhere*, they occur normally lodged in 

 the spaces of a peculiar tissue which forms an adventitia to some 

 of the arteries. They are only discharged into the blood as a 

 result of special stimuli. In Vertebrates they occur to a marked 

 extent in the peculiar adventitia of the blood-vessels of the spleen. 



It is noticeable that I have so far failed to find rose-staining 

 granules in endoderm cells, though I have examined the lining cells 

 of the alimentary canal and of its glands in very diverse animal types. 



The cells of the excretory organ (end-sac of Daphnia) contain 

 granules which have a remarkable affinity for methylene-blue and 

 stain a deep opaque blue. 



* Journal of Physiology, 1892. 



