DISSECTION OF HOLOTHURIANS. 219 
Laboratory Work.—The Holothurians are easily dissected by cutting 
the body opening longitudinally, and pinning the specimen down in a 
dissecting-pan, with wax on the bottom for holding the pins. The 
calcareous plates can be extracted from the body-walls by being placed 
in a solution of potash and mounted in balsam as microscopic objects. 
Nots.—In opposition to the classification on pp. 215-218 it is pos- 
sible that the Apoda are a later, much modified group, and derived 
from the Pedata, which'may have included the primitive Holothurians. 
LITERATURE. 
G. J. Romanes. Jelly-fish, Star-fish, and Sea-urchins. 1885. 
J, Miller. Seven Memoirs on the Larve and Development of 
Echinoderms. Berlin, 1846-1854. 
A, Agassiz. Embryology of the Star-fish. 1864. 
E. Metschnikof. Studien tiber die Entwickelungsgeschichte der 
Echinodermen und Nemertinen. St. Petersburg, 1869. 
H. Iudwig. Morphologische Studien an Echinodermen. Leipzig, 
1877-1878. 
Sea-cucumber (Synaptu). .A, larva; B, young farther advanced, with the Syn- 
apta (fd) poo vithins C, young become free (after Miller); D, adult Synapta 
Tkinweley del.). 
