308 SUMMARY OF CURRENT RESEARCHES RELATING TO 



axis of the instrument in place of the solid cylinder P. If the apparatus 

 stand on a blackened glass plate and the image of a signal be reflected 

 down the tube, two images may be seen when the eye is placed over the 

 vertical illuminator, one from the optical flat and the other from the 

 blackened glass plate; by turning the screw S these images may be 

 brought into coincidence, and it is found that this method of adjustment 

 is sensitive to 2' of arc. Plates may thus be cut the surfaces of which 

 do not depart more than 2' from parallelism. The principle under- 

 lying the application of the instrument is that a crystal suitably mounted 

 on any of the holders may be rotated in two directions at right angles 

 to each other, one of the axis of rotation being that of the cylinder P. 

 By means of these two movements it is possible to bring any desired 

 direction in the crystal normal to the grinding surface. 



Investigating the Life-history of the Sporozoa of Spatangoids.* 

 Helen L. M. Pixell-Goodrich obtained Echinocardium cordatum from 

 Naples, Plymouth, and Port Erin. A little hole is made in each side of 

 the test. The ccelomic fluid can then be poured out into a suitable 

 vessel and examined with a binocular Microscope. Afterwards the 

 inside of the testis carefully washed out with sea-water introduced by 

 a pipette through one of the holes and the washing collected and examined 

 iu a similar way. The cysts containing early stages are generally free 

 in the cavity and readily distinguished by their opacity. The cyst walls 

 of those ripe with spores, where not covered with amcebocytes,.are so 

 translucent that the spherical mass of crystals shows up with great clear- 

 ness in the interior. Nearly all the work was done on living parasites, 

 though films and sections were also made. Hot corrosive sublimate and 

 acetic acid mixture fixed the sporozoite nuclei of the ripe spore satisfac- 

 torily. In studying differences in the shapes of the tails it was found 

 best to overstain with iron-hasniatoxylin or haematein, which are fairly 

 readily taken up by the epispore, but readily lost again on differentiating 

 with iron alum. Orange G and nigrosin also stain the epispore, but 

 not very easily. Unless well stained the tails are practically invisible 

 in Canada balsam. For rough comparison, Stephen's ink was found 

 very convenient for staining the tails of fresh spores. 



(4) Staining: and Injecting - . 



Vital Staining of the Nucleus.t — A. M. Przesmycky used neutral 

 red for staining intra vitam the nuclei of protozoa and metazoa. The 

 nucleus behaved differently. It might stain uniformly ; the staining might 

 be irregular, some parts being dark, others light. In a third class, the 

 staining clearly differentiated between the chromatin and the achromatin. 

 It, was noticed that all the organisms which stained well during life 

 decolorized directly they died. The results were, that the stained 

 and living nucleus was able to divide, and that after death it decolorized 

 though it remained in the staining fluid. The different substances in 

 the living nucleus stain quite distinctly, e.g. chromatin and achromatin. 

 The living nucleus has a greater affinity for neutral red than the proto- 

 plasm, as it stains more strongly and decolorizes more slowly. 



* Quart. Journ. Microscop. Sci. lxi., 1915, pp. 81-104 (1 pi.) 

 + C.R. Soc. Biol, lxxviii. (1915), pp. S3-6. 



