112 The Microscope. 



One point which remains unsolved relates to the relation 

 of the mouth to the brain in the vertebrates and invertebrates. 

 In the latter the oesophagus passes through the nervous cord 

 (vid); fig. 3, in the vertebrates no such perforation occurs. 

 There are two prominent theories to account for this. One sup- 

 poses that the supra-cesophagal ganglion of the invertebrates 

 has disappeared from the vertebrate series, and that our brain 

 corresponds with the infracesophagal ganglion of the lobster or 

 grasshopper. The other takes the ground that, in the evolution 

 of the vertebrates, the invertebrate mouth has disappeared, and 

 a new one has formed. This view seems the more probable. 

 It generally strives to recognize the old mouth in the otherwise 

 inexplicable infundibulum and pituitary body. It supposes 

 the existing mouth to have arisen by a coalescence of gill clefts, 

 a view which receives much probability from the mode of origin 

 and development of the upper and lower jaws. 



GOLD AND SILVER FERNS. 



L. G. DOANE. 



UPON a slip of glass put a drop of liquid Auric Chloride or 

 Argentic Nitrate, with half a grain of metallic zinc in the 

 Auric Chloride, and copper in the silver. A growth of exquis- 

 ite gold and silver ferns will grow beneath the eye. 



A HANDSOME FINISH FOR SLIDES. 



J. E. HAYS, M. D. 



TAKE one of the packages of " Gold or Silver Paints " put up 

 by Wells and Richardson, of Burlington, Vt., and sold in 

 connection with their " Diamond Dyes" and add it to one-half 

 an ounce of the best Damar Varnish, warming the varnish so 

 as to make the paint mix with it well, and apply with fine 

 brush. The paint will settle to the bottom upon standing, but 

 by warming a little and shaking well it is diffused again. This 

 makes a very pretty finish and adds strength to the cover cement 



as well. 



■++*• 



We have a large number of preparations in our cabinet, 

 mounted by Cole, of London. They were all finished with 

 white zinc and not a single slide is imperfect to-day. 



