296 LIONEL JAMES PICTUN. 



help, aud I am also much indebted to Professor Eisig. I have 

 to thauk Professor Lankester and Mr. E. S. Goodrich of 

 Oxford for suggestions and criticism. 



Appendix. 



Note on intra-vitam Staining of Nuclei with 

 Carmine in Sea-Water. 



The question whether nuclei can be stained whilst alive is 

 still undecided. Galeotti (' Z. f. wiss, Mikr./ xi, p. 172) says 

 that the processes of coloration in the normal condition "mai 

 si mostrano nel nucleo.^' Pfeffer (' Untersuch. Bot. Inst. 

 Tiibingen/ vol. ii, p. 325) says that nuclei will only stain with 

 methylene blue after the cells have been damaged. Bethe 

 (* Biol. Central./ xv, 1895, p. 141) states that the epithelial 

 nuclei of a living piece of a Ctenophore may be stained with 

 methylene blue. Lauterborn (' Untersuchungen uber Dia- 

 tomen/ Leipzig, i, 1896, p. 36) speaks of seeing moribund 

 diatoms, the nuclei of which were stained, move along in the 

 field of the microscope. Finally, Przesmycki (' Biol. Central.,' 

 xvii, 1897, p. 321), writes of " intra-vitale Farbung des Kerns 

 uud des Protoplasmas," with " neutral red " and methylene 

 blue by means of a special technique, to be explained in a 

 later paper. 



During my work on the heart-body I had occasion to cut 

 sections of Siphonostoma which had been for a week in ajar 

 of aerated sea-water in which some powdered carmine had been 

 stirred up, and was surprised to find that in sections mounted 

 without further stain the nuclei and especially the nucleoli of the 

 gut-cells were coloured red. The fixative used was corrosive 

 sublimate and acetic acid, aud to the action of this on the car- 

 mine in the gut of the animal, Dr. Meyer attributed the stain. 

 I found, however, that the stain still occurred after fixation in 

 90 per cent, alcohol ; and even in living tissue ^ some nuclei 

 were found stained pink. The majority of the gut cells are so 

 loaded with granules in the fresh state that it is impossible to 

 ' Ciliary movemeut was going on in the preparation. 



