150 G. T. HARKIS ON THE COLLECTION AND 



and as a good general stain is all that is required for systematic 

 work it does not much matter which is used. I have used 

 principally para-carmine, carmalum and haemalum of Mayer's 

 formulae; the last of which I prefer on account of its better 

 visual properties, also because it stains exceptionally well objects 

 that have been fixed with osmic acid. I may here mention that 

 haeniatoxylin has been regarded by some workers as a fugitive 

 stain ; why, I am unable to discover. I attempted to bleach 

 some slides that had been over-stained by exposing them for some 

 months in a window with a south aspect, and at the end of that 

 time withdrew them as hopelessly permanent. They should have 

 faded, according to all the authorities, but much to my disgust 

 they did not. 



For unstained objects I use excavated slips, and a 2^-per-cent. 

 solution of formalin. A ring of old, fairly thick gold size is run 

 round the edge of the hollow and allowed to become nearly dry, at 

 least dry enough to retain the impression of a scratch made with 

 a needle. The selected portion of the hydroid colony is placed in 

 the cell, and 2|-per-cent. formalin solution added until a full cell 

 with a convex surface to the fluid is obtained. The cover-glass is 

 then placed in position, expelling the superfluous formalin. Under 

 a mounting microscope, with a strong blunt needle, the cover- 

 glass is pressed into intimate contact with the ring of gold size, 

 until it can be seen that no lacunae exist between it and the cover- 

 glass. The extraneous formalin is now removed and the slide 

 allowed to dry, when several rings of gold size may be applied. 

 Slides so prepared have attained the comparative antiquity of 

 sixteen or eighteen years without showing any deterioration. 



As this paper has been prepared with the object of placing 

 practical information before those desirous of devoting some 

 attention to our hydroid fauna, it may not be considered alien to 

 the subject if I refer briefly to various localities of which I have 

 personal knowledge, from collecting more or less frequently in 

 them ; merely premising that my acquaintance with them as 

 collecting-grounds has been more by accident than design, and I 

 have no wish to suggest that they are any more desirable from 

 the collector's point of view than numbers of others unknown to 

 me. In North Wales my collecting-stations have been Llandudno, 

 Menai Straits, Criccieth and Barmouth. Llandudno and Criccieth 

 are excellent grounds. The rocks at I4andud.no under the Great 



