DEVELOPMENT OF AMPHTUEA SQFAMATA. 151 



13. Perriek, E. ^"Ueclierches sur ['organisation des l^toiles de Mer," 



' Comptes Rendus,' tome cii, 1886, p. 1146. 



14. Perkier, E. — " Memoire sur I'organisation et le developpement de la 



Comatula de la Mediterranean," ' Archives de Zool. Experimentale,' 

 1886. 



15. Prouho, M. — " Sur le developpement de I'appareil genital des Oursins," 



' Comptes Hendus,' tome civ, 1887. 



16. Russo, A. — "Embryologia d'Amphiura squamata," ' Rendiconti 



delle Societa Reale di Napoli,' tome v, 2nd series. 



17. Russo, A. — " Recerclie citologiche sugli elementi seminale delle 



Ophiurege," ' Internationale Monats. fiir Anatomic und Physiologic,' 

 vol. vii, 1890. 



EXPLANATION OF PLATES XVI, XVII, & XVIII, 



Illustrating Mr. E. W. MacBride's paper " On the Develop- 

 ment of the Genital Organs, &c., of Amphiura 

 squamata." 



List of Abbreviations > 



C. Ccelom. ffen. b. Genital bursa. ge7i. r. Genital rachis. k. r. Kohler's 

 "haemal" ring. m. p. Madreporic pore. msch. Mesenchyme-cells fllliug the 

 ccelom. muse. buee. External muscles of mouth, muse. int. Interradial 

 muscle of disc. muse. r. Muscles of the arm. ov. g. Ovoid gland, new. rg. 

 Nerve-ring. p. c. Pore canal, rad. nerv. Radial nerve, sinus a. Aborai 

 sinus, sinus b. Axial sinus, sinus c. Ampulla of the stone canal, sinus spin. 

 Epineural sinus, sinus rad. perih. Radial perihsemal sinus, sinus perist. 

 Peristomal sinus, sh Shrinkage space, st. e. stone canal, w. v. r. Water 

 vascular ring. 



Figs. 2 E and 6 d are diagrams. The outlines of all the rest have been 

 drawn with the camera lucida, and except where otherwise stated are magnified 

 34.0 diameters, and taken from sections parallel to the axis of the stone canal 

 of specimens preserved in osmic acid followed by Miiller's fluid. 



Fig. 1. — From an individual -86 mm. in diameter. Magnified 130 diameters. 

 Osmic alone, sitius rad. perih. Radial perihsemal sinus, sinus ep. n. Epi- 

 neural sinus, sinus perist, Circumoral sinus. 



Fig. 2 a. — Section of ovoid gland and surrounding structures of an adult- 

 gen. r. Portion of genital rachis where it passes into ovoid gland, sk. Shrink 



