148 JOHN BEARD. 
the physiological study of these organs, they will have done a 
great deal. For in spite of the many brilliant researches on 
the structure of these branchial sense organs, which have 
undoubtedly told us much about their structure and distribu- 
tion, we cannot till now be said to have gained a clearer insight 
into their truenature than we possessed after Leydig’s researches. 
This honoured histologist and zoologist showed that they were 
really sense organs, but there the matter has remained for 
thirty-five years. 
My researches on the lateral line were commenced over 
two years ago in Professor Semper’s laboratory in Wirzburg. 
In consequence of difficulties with the only material I then had, 
viz. embryos of Teleostei, they led to very little result. After- 
wards they were for a time laid aside for other work. Although 
the results of the work in Wurzburg were very barren, being 
made in what appeared to be a dreary and empty field, still 
my gratitude is none the less due, and is here expressed, to 
Professor Semper for his untiring advice and assistance. 
To Professor Milnes Marshall, in whose laboratory the 
later researches on Elasmobranchs were made, my acknow- 
ledgments are due not only for the privilege of the use of 
his library of zoological works, but also for his valuable 
assistance, criticism, and advice. I also wish to express 
my best thanks to Professor Wiedersheim for good counsel, 
and to my friend Dr. L. Will, who very kindly made a 
number of useful extracts from Gdtte’s great Unke work, a 
work which was inaccessible to me in Manchester. 
LITERATURE OF THE BRANCHIAL SENSE ORGANS. 
1. Batrour, F. M@i—‘A Monograph of the Development of Elasmobranch 
Fishes,’ 1878. 
2. Batrour, F. M.—‘ Comparative Embryology,’ vol. ii. 
3. BEarp, J.—“ On the Segmental Sense Organs, and on the Morphology of 
the Vertebrate Auditory Organ,” ‘ Zool. Anz.,’ Nos. 161, 162, 1884. 
4, Brarp, J.—‘*On the Cranial Ganglia and Segmental Sense Organs,” 
‘Zool. Anzeig.,’ 192, 1885. 
