DISSECTION OF UOLOTUURIANS. 



219 



Laboratory Work. The Holothurians are easily dissected by cutting 

 the body opening longitudinally, and pinning the specimen down iu a 

 dissecting-pau, with wax on the bottom for holding the pins. The 

 calcareous plates can be extracted from the body-walls by being placed 

 iu a solution of potash and mounted in balsam as microscopic objects. 



NOTE. In opposition to the classification on pp. 215-318 it is pos- 

 sible that the Apoda are a later, much modified group, and derived 

 from the Pedata, which may have included the primitive Holothuriaus. 



of 



LlTERATUKE. 



O. J. Romanes. Jelly-fish, Star-fish, and Sea-urchins. 1885. 



J. Mutter. Seven Memoirs on the Larvae and Development 

 Echiuoderms. Berlin, 1846-1854. 



A. Agassiz. Embryology of the Star-fish. 1864. 



E. Metschnikoff. Studien liber die Entwickelungsgeschichte der 

 Echiuodermen uud Nemertinen. St. Petersburg, 1869. 



H. Ludwig. Morphologische Studien an Echiuodermeu. Leipzig, 

 1877-1878. 



Sea-cucumber (Synapta). A, larva; B, young farther advanced, with the Syn- 

 apta (fd) growing within; C, young become free (after Muller); D, adult Synapta 

 (Kingsley del.). 



