DEVELOPMENT OE DISTIOHOPOEA VIOLAOEA. 45 



The Early Stages in the Development of Disti- 

 chopora violacea, with a Short Essay on 

 the Fragmentation of the Nucleus. 



By 



Sydney J. Hlckson, M.A. Cantab, et Oxon., D.Sc.IiOnd., 



University Lecturer on the Morphology of Invertebrates ; Fellow of 

 Downing College, Cambridge. 



With Plate IV. 



The material upon which I have made my investigations was 

 in part collected by me in N. Celebes, and in part by Professor 

 A. C. Haddon in Torres Straits. Some of the specimens were 

 treated with strong alcohol alone, others with corrosive sub- 

 limate followed by alcohol. For decalcification I have entirely 

 used nitric acid. 



I have tried a great many difi'erent stains and combinations 

 of stains. Borax carmine, Biondi's fluid, methyl green, and 

 hsematoxylin all give fairly good results; but I find that the 

 best treatment is to place the sections, when fastened to the 

 slide, in a strong solution of eosin in 90 per cent, spirit for an 

 hour, then to wash in 90 per cent, spirit and stain in weak 

 hsematoxylin for twenty minutes. This treatment gives a 

 beautiful double stain which shows the nuclei and the chromatin 

 granules better than I have seen them in any preparations 

 treated with carmine. 



My researches were entirely carried on in the morphological 

 laboratory at Cambridge. 



VOL. VI. 5 



