OBSERVATIONS ON THE NUCLEOLI IN THE CELLS OF HYDRA 

 FUSCA. By C. E. Walker and Alice L. Embletox. (From the 

 Laboratory of Cytology, University of Liverpool.) (With One Plate.) 



{Received for puhlvat ion, 25th July 1908.) 



Methods and Material. 



Hydra fusca was used throughout in the observations described here. 

 The hydrae were fixed with Flemming's fluid (strong formula). Dehydra- 

 tion, embedding in paraffin, and the various other processes, were carried 

 out according to the strictest cytological methods. 



The following two processes of staining were chiefly employed, and 

 only the results obtained by these are described here. 



A. Saturated solution of basic fuchsin in 80 per cent, alcohol, plus 

 a few drops of liquor ammon. fort., for about two minutes. Rinse in water 

 and 30 per cent, alcohol, and water again, getting rid of part of the red 

 stain so as to leave the sections pink. Methylene blue (aqueous solution) 

 for about a minute ; rinse in water. Unna's orange tannin until no more 

 blue clouds are to be seen. Dehydrate, clear in xylol, mount in Canada 

 balsam. 



B. Saturated solution of saflranin in 80 per cent, alcohol, with a few 

 drops of liquor ammon. fort., for a quarter of an liour, followed by methy- 

 lene bhie and Unna's orange tannin, as in first method. 



Observations. 



The nucleolus dealt with here is the " true nucleolus." It is a body 

 generally spherical in shape, occasionally oval, bounded bj'^ a definite 

 membrane, the contents being usually homogeneous, or finely granular in 

 structure.^ 



The nucleoli in the cells of hydra, both in the ectoderm and in the 

 endoderm, are very striking and definite. Generally only one nucleolus is 

 to be seen in the nucleus, but in some cells we have found two, or even 

 more, of diflerent sizes. While within the nucleus, the nucleoli stain dark 



' See Wilson, "Tlie Cell in Develoi^ineiit and Inheritance," p. 34; Macniillan, 

 London and New York, 1904. Walker, "Tlie Essentials of Cytology," pp. 12 and 13; 

 Constable, London, 1907. 



