GEEGAEINID^ 81 



To follow these movements, a small quantity of sepia should be 

 added to the fluid in which the specimen is teazed out ; or the 

 Gregarines may be examined in normal saline solution in, which either 

 Indian ink or carmine has been rubbed down until a black or deep 

 red colour is obtained. As they move forward, the Gregarines will 

 then be seen to leave a light track which shows up clearly in the 

 darker medium. With a strong lens, in the interior of this light 

 track long rows of colour granules may be seen, which appear to be 

 clinging to the surface of a fine hyaline thread. These strings of 

 granules sometimes appear to unite to form bundles. 



This phenomenon is explained by the fact that, when in motion, the 

 Gregarines secrete thin homogeneous threads of a sticky gelatinous 

 substance, which cling together at the hinder end of the organism 

 to form a sort of stalk. The refractive index of these threads corre- 

 sponds so completely to that of the normal saline solution that, until 

 the colour grains are added, they are not directly distinguishable 

 from it. They may, however, be rendered directly visible in the 

 following manner : A carmine preparation containing Gregarines is 

 put into a damp chamber for about two hours. The gelatinous stalks 

 of the moving Gregarines will then become so long that they may 

 be perceived with a low-power lens or even with the naked eye. All 

 the grains of carmine, with the exception of those clinging to the 

 threads, are now removed by carefully washing out the preparation 

 with clean normal saline. This is done by adding fresh liquid at one 

 edge of the glass while the coloured fluid is drawn off from the 

 opposite edge by means of filter paper. By this means, the stalks 

 become isolated and may now be stained with methyl-violet, though 

 they should first be fixed in alcoholic solution of mercuric chloride 

 In changing the liquid, the flow should correspond as far as possible 

 with the direction in which the Gregarines are moving, as their 

 delicate stalks may otherwise be damaged. 



The structure of the living Gregarine should now be carefully 

 studied. The cuticle will be found to be thicker, and the hyaline 

 ectoplasm thinner, than in the monocystic Gregarines of the earth- 

 worm. There is the same fine, longitudinal striation of the cuticle ; 

 and circular muscle-fibrillae, arranged somewhat further apart, are 

 also present between the ecto- and the endoplasm. With a high- 

 power lens, a light homogeneous layer becomes visible between the 

 cuticle and the ectoplasm, which is subject to considerable variation 

 in thickness and is usually most clearly discernible during the forward 

 gliding movements. This is the slime-secreting layer, and from it, 

 during movement, gelatinous secretion is conveyed by means of longi- 

 tudinal slits in the cuticle. The endoplasm contains a varying 

 proportion of round granules of high refractivity. In the larger 

 6 



