354 



MR. G. S. BRADY'S MONOGRAPH OF 



taken, and afterwards picked out one by one. By this method the animal structure 

 contained in the shell is almost always entirely destroyed, or at any rate is so far decom- 

 posed as to be quite unfitted for any critical examination. On this account I have often 

 been unable to give anatomical descriptions of deep-water species. There can be no 

 doubt that by proper treatment of the dredged material shortly after its removal from 

 the sea-bed, the contained Microzoa might to a large extent be obtained in a serviceable 

 and perfect condition ; while, in the case of material taken in the hand-net or towing-net, 

 it need never be a difficult matter to separate the Ostracoda with the help of a simple 

 pocket-lens. 



As to the manipulation of the animals and their preparation for the microscope, it is 

 seldom that much difficulty will be experienced in separating the valves by means of 

 fine needles, and then detaching the contained animal ; the various organs are rendered 

 much more distinct by immersion for a short time in a solution of potash, by which the 

 oleaginous and granular constituents are to a great extent removed, the chitinous 

 structures remaining unaffected. If it be desired to mount permanently the dissection 

 thus made, the best medium for the purpose is a compound of glycerine and gelatine 

 with a slight addition of arsenic, the formula for which is given below*. This preparation 

 has the advantage of becoming fluid at a low temperature, of retaining its moisture 

 sufficiently without any cementing of the glass cover, and of being colourless and very 

 easy of application. 



The geographical and bathymetrical distribution of the Ostracoda is a matter of the 

 greatest interest as illustrating the probable conditions under which the various fossili- 

 ferous strata have been deposited. The data at present at our command are somewhat 

 scanty, and negative evidence must be taken for no more than it is worth ; but some 

 portions of the British coasts, as, for example, those of Northumberland and Durham, 

 and the Erith of Clyde, have been pretty diligently dredged and investigated with a 

 view to the study of these organisms. I have therefore brought together, in a tabular 

 form at the end of the monograph, the principal districts in which the marine species 

 have been examined, and have endeavoured roughly to indicate their frequency and 

 range of depth by means of signs, as explained in the Table. The two final columns 

 indicate the occurrence or non-occurrence of the species in the Scandinavian seas, and 

 in the Tertiary or Posttertiary deposits of Great Britain and Norway. Por the informa- 

 tion given respecting the recent Scandinavian species I am indebted entirely to Herr G. 

 O. Sars and Professor Lilljeborg; the column relative to fossil species owes its com- 

 pleteness chiefly to the labours of Messrs. Crosskey and Bobertson. 



I must here express my great obligations to many kind friends for the communication of 

 dredgings and specimens from various parts of the country, — to Mr. J. Gwyn Jeffreys and 

 Mr. C. Spence Bate, Mr. E. C. Davison, of Sunderland, Mr. S. S. Stoddart, of Bristol, and 



* Take any quantity of Nelson's gelatine, and let it soak for two or three hours in cold water which has previously 

 been saturated with arsenious acid ; pour off the superfluous water, and heat the soaked gelatine until melted. To 

 each fluid-ounce of the gelatine add one drachm of alcohol, and mix well ; then add a fluid-drachm of the white of an 

 egg ; mix well while the gelatine is fluid but cool. Now boil until the albumen coagulates and the gelatine is quite 

 clear. Filter through fine flannel and to each fluid-ounce of the clarified gelatine add six fluid-drachms of Price's 

 pure glycerine, and mix well. — Carpenter' s Microscope and its Revelations, .3rd edition, p. 775. 



