MYZOSTOMIDA FROM THE RED SEA. 107 



lying ventral to the stomach. The nephvidia run side by side 

 ventral to the stomach for a short distance, but in the posterior 

 region of that organ slope upwards again, finally lying lateral to 

 the rectum just before opening into it. 



Nervous System. 



I was able to make out very little of the nervous system^ of this 

 species, as the peripheral nerves were only very poorly stained in 

 my sections. The central nerve-mass was, however, distinct and 

 occupied the same position as in other species, that is to say the 

 centre of the body, in the region between the second and fourth 

 pairs of parapodia. 



This typical concentration of the central nervous system is a 

 point of interest, since it shows that the, elongated form of 

 M. crosslandi is probably not a primitive character ; the arrange- 

 ment of the intestinal branches and other organs also indicates 

 that this species is derived from some form possessing a more 

 radial symmetry. 



This is probably also true of allied species, such as M. nanseni 

 and M. folium. 



List of References. 



1. Beard, J. — " On the Life-History and Development of the 



Genus Myzostoma (F. S. Leuckart)," Mitth. Zool. Stat. 

 Neapel, Bd. v. 1884, p. 544. 



2. . " The Nature of the Hermaphroditism of Myzostoma," 



Zool. Anz. Bd. xvii. 1894, p. 399. 



3. BouLENGER, 0. L.— "The 'Suckers' of the Myzostomida?." 



Zool. Anz. Bd. xxxvii. 1911, p. 346. 



4. Clark, H, L. — " A new Host for Myzostomes." Zool. Anz. 



Bd. XXV. 1902, p. 670. 



5. Coventry, A. F.— " The Application of Mr. G. W. Smith's 



Theory of Dwarf Males to Myzostoma." Ann. Mag. Nat. 

 Hist. ser. 8, vol. v. 1910, p. 378. 



6. Fedotov, D. — " Protomyzostomum polynephris, eine neue 



Myzostomidenart." Zool. Anz. Bd. xxxix. 1912, p. 649. ^^ 



7. Graff, L. v. — "Das Genus Myzostoma (F. S, Leuckart)." 



Leipzig, 1877. 



8. . " Report on the Myzostomida collected during the 



Voyage of H.M.S. 'Challenger' during the Years 1873- 

 76." Rep. ' Challenger' Exped. vol. x. Pt. 27, 1884. 



9. . Supplement to the preceding Report. Rep. ' Chal- 

 lenger ' Exped. vol. XX. Ft. 61, 1887. 



10. Leuckart, F. S.— " Bericht liber die achte Yersammhmg 



deutscher Naturforscher und Aerzte zu Heidelberg im 

 September 1829." Oken's Isis, 1830, Heft v. p. 612. _ 



11, . " Zoologische Bruchstiicke. III. Helminthologische 



Beitrage.'' Programm zur Eroffnung der Wintervorles 

 ungen iu Freiburg i. B. 1842, p. 5. 



