346 Proceedings of the Royal Society of Edinburgh. [Sess. 
The conclusion stated at the beginning of this section, that the 
sympathetic system is secondary in its development to the central nervous 
system, is interesting in connection with Gaskell’s view of the relationship 
of the central nervous system of vertebrates to that of annelids and 
arthropods. In his book, The Origin of Vertebrates, Gaskell describes the 
central nervous system of the vertebrate as the homologue of the nervous 
system of the annelid or arthropod. Reasoning from Gaskell’s standpoint, 
the homologue of the invertebrate nervous system in the vertebrate would be 
the most primitive portion of the vertebral nervous system, and the first to 
develop. This theory is supported by my results, which, as already stated, 
point definitely to the sympathetic system being secondary in formation. 
I wish to acknowledge my deep indebtedness to Professor Noel Paton, 
under whose guidance I made this research, both for suggestion and help 
during my work, and for helpful criticism of this paper. 
DESCRIPTION OF ILLUSTRATIONS. 
Plates I. and II. consist of sepia drawings ; III. and IY. of photographs. 
LIST OF REFERENCES. 
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(2) Remak, Uber ein selbstandiges Darmnervensystem, Berlin, 1847. 
(3) Hensen, “Zur Entwickelung des Nervensystems,” Virchow's Archiv, 1864. 
(4) His (senior), Untersuchungen iiber die erste Anlage des Wirbelthierliebes, 
1868. 
(5) Gotte, Die Entwickelung sgeschichte der TJnke, 1872. 
(6) Balfour and Foster, Grundzuge der Entivickelungsgeschichte, 1876. 
(7) Balfour, “ Development of Elasmobranch Fishes,” Journal of Anatomy and 
Physiology , 1877. 
(8) Schenk and Birdsall, “ Die Entwickelung des sympathicus,” Mitth. aus d. 
ernbry. Inst, in Wien , vol. T, 1879. 
(9) Onodj, “Uber die Entwickelung des sympathetischen Nervensystem,” Archiv 
fur mik. Anat., vol. xxvi. 
(10) Paterson, “The Development of the Sympathetic Nervous System in 
Mammals,” Proceedings of the Royal Society , 1890. 
(11) His (senior), “ Histogenese und Zusammenhang der Nervenelemente,” 
Archiv filr Anat., Abtheg. 1890. 
