PREFACE. IX 



of preparations, which have been since demon- 

 strated at the meeting of the Royal Microscopical 

 Society, on November 25th. 



All the plates have been most faithfully and 

 skilfully reproduced by Messrs. Vincent Brooks, 

 Day, & Son. 



In conclusion, I owe much to Professor Gerald 

 F. Yeo, of King's College, London, for many 

 valuable criticisms ; and to my colleague, Mr. 

 Herroun, for his kindness in reading the proof- 

 sheets. 



EDGAR M. CROOKSHANK. 



24, MANCHESTER SQUARE, W., 

 December, 1885. 



