116 Papers from the Marine Biological Laboratory at Tortugas. 



THE MUSCULAR SYSTEM. 



Although the body-wall is thick and exceedingly stiff the starfish 

 is very mobile. The aboral musculature is shown in fig. 4, where it will 

 be seen that in each arm there are three principal muscle bands, each 

 with numerous branches. 



GENERAL. 



Of the organs which are described and figured those which seem of 

 greatest interest are the intestinal cseca. These, as above stated, were 

 found in some instances to be greatly distended, stimulation causing 

 their contraction. Upon allowing individuals, from which the aboral 

 wall had been removed, to remain undisturbed in sea-water, the organs 

 again became distended and later contracted of their own accord. In 

 this behavior we have support to the idea of the analogy of the intestinal 

 ca;ca of the starfish to the respiratory trees of the holothurian, an idea 

 which has been based in the main upon the similarity of position of these 

 organs. 



LITERATURE. 



Agassiz, a. 1877. North American Starfishes. Mem. Mus. Comp. ZooL Harvard 



College. Vol. v. 

 Clark, H. L. 1901. The Echinoderms of Porto Rico. U. S. Fish Commission 



Bulletin for 1900. Vol. 11. 

 Linck, J. H. 1733. De stellis marinis. Lipsiae. 



MiJLLER AND Troschel. 1 842. System der Asteriden. Braunschweig. 

 Perrier, E. 1875. Revision des Stellerides. Arch. zool. exp6rim. et gener. T. iv. 

 Studer, Th. 1880. Ueber Geschlechts dimorphismus bei Echinodermen. Zool. 



Anzeiger, p. 545. 

 ViGUiER, C. 1878. Anatomic comparee du squelette des Stellerides. Arch. zool. 



exper. et gener. T. vii. 



FIGURES. 



Figures i to 6 were drawn with crayon on Ross's stipple paper to the full size 

 of the object and have been reduced two-thirds in reproduction. 



Abbreviations. 



an., anus. pol. ves., Polian vesicle. 



amp., ampulla. pyl. coec, pyloric caecum. 



card. St., cardiac portion of stomach. rad., radial canal. 



i. p., interradial septum. r. c, ring canal. 



madr., madreporite. resp., intestinal caecum. 



mad. can., stone canal. retr., retractor muscle of stomach. 



op. resp., opening of intestinal caecum. Tiedm., Tiedemann body. 



ov., ovary. ts., testis. 



mes., mesentery. 



