TRANSACTIONS OF SECTION D. 785 



\9hen the ferns are nearly exhausted, the gathering mania is passing from ferns to 

 primroses (see remarks on No. 941. D. R.). — The remarks on No. 1766 are 

 applicable also to this species as a plant of the Western Islands, &c. (D. A. B.). 



1806. Osmunda regalis, E. Himterston, Ayrshire; formerly luxuriant on the 

 cliffs and low gi-ound facing the sea, but now extinct, the plants being carried 

 away (D. L.).- — Portincross, Ayrshire ; a few plants formerly grew here, but were 

 all dug up and carried away (D. A. B.). — Shewalton Moss, Dundonald, Ayrshire; 

 extinct, the moss being reclaimed (J. S.).— Island of Cumbrae, Buteshire; 

 formerly plentiful in places ; this fern has now almost entirely disappeared, being 

 carried away with 1782 and others (D. R.). — Island of Arran, Buteshire; up till 

 1860 abundant in many places, but now extinct, or nearly so, having been carried 

 away by cartload and boatload (D. L.). Roots are sometimes still offered for sale 

 to visitors in the island (U. A. B.). — Achacha District, Benderloch, Argyllshire ; 

 formerly plentiful, but now none has been seen for twelve or fourteen years, the 

 roots having been continually sought after and removed by collectors (W. A. S.). 

 —Loch Fyne District, Argyllshire; becoming extremely rare through ruthless 

 coUections'for sale (W. A. §.)■ — Western Islands, &c. ; see remarks on No. 1766, 

 very applicable to this species (D. A. B.). 



1822. Lycopodium Selago, L. Mons, near W^est Kilbride, Ayrshire; much 

 less common than formerly, probably owing to drainage (D. A. B.). — W^estem 

 Islands, &c. ; occasionally exposed for sale in the streets of Glasgow. As No.. 

 1766, &c. (D. A. B.). 



Department of Zoology. 



1. Presentation de Planches inedites de Zoologie concernant les RechercTiej 

 du Yacht ' VHirondelle.' Par Baron Jules de Guerne. 



2. Crustaces Copepodes des Eaux sursaturees de Sel de la France et des 

 Canaries. Par Baron Jules de Guerne. 



I 



3. Observations on the Development of the Posterior Cranial and Anterior 

 Spinal Nerves in Mammals. By Arthur Robinson, M.I)., Senior 

 Demonstrator of Anatomy at the Oivens College, Manchester. 



1. In cat and rabbit embryos of eleven proto-vertebral somites, and in mouse 

 and rat embryos of a similar stage of development, a continuous cord of nerve-cells 

 extends backwards from just within the posterior part of the auditor}- depression 

 along the dorso-lateral angle of the medulla and spinal cord. At this period the 

 cord of cells is connected with the dorsal extremity of the neural tube by a series 

 of cellular strands, which are so numerous and so closely opposed that they almost: 

 form a continuous lamina, which is only one cell thick. 



2. During the period of formation of the secondary optic cup this cellular cord 

 (a) loses its connection with the dorsal extremity of the neural tube ; (b) becom.ee- 

 thickened in the region between the auditory vesicle and the first somite; (o) 

 remains relatively small from the first to the fourth somite ; (d) beyond the 

 fourth somite it gives origin to a series of swellings, the spinal ganglia. 



3. At a later period, in cat embryos of 9 mm., in mice of from 2i-5 mm., and 

 in rat embryos of a similar stage of development, the cord of cells in the region of 

 the first four somites is enlarged in three places. One enlargement is situated in 

 relation with the fourth somite, which is in the cervical region ; the other two are 

 in relation with the second and third somites, which belong to the occipital region. 

 The cellular cord is also enlarged in the region of the first somite, but this enlarge- 

 ment is continuous with the enlargement in the pre-^mitic region, and cannot be 

 distinctly separated from it. 



1802. 3 E 



