10 THE VOYAGE OF H.M.S. CHALLENGER. 



the latter noted on the minute male the presence of two hooks behind the mouth opening. 

 Vejdovsky ^ investigated anew the structure of the male Bonellia, and discovered the 

 central nerve-cord, which had till then been overlooked. I then ^ described for the first 

 time the oesophageal nerve-ring, the alimentary canal without mouth or anus, and the 

 two rudiments of the anal vesicles. In a very exhaustive memoir Spengel ^ has given 

 figures and desci'iption of the structure of the male BoneUia, yet both this naturalist and 

 Greefi" have overlooked the rudimentary anal vesicles which I have here figured in 

 PL II. fig. 10. After Spengel's excellent description it seems to me unnecessary to 

 enter further into the discussion of the anatomical details, and I therefore simply refer to 

 the fio'ures. 



&^ 



B. Gephyeea ach.5;ta. 



A. Gepliyrea without seta;. 



Genus 5. Phascolosoma, F. S. Leuckart. 



"The longitudinal musculature is continuous and not divided into distinct bands. 

 There are numerous tentacles arranged in a circle or in groups round al;)out the mouth. 

 The intestine is spirally coiled. The " intestinal spiral " (Darmspira) in the posterior 

 portion of the body quite unattached. Hooks may be absent. There are two 

 free segmental organs. Eggs spherical. Two to four retractors of the proboscis. 

 Found in aU seas. 



G. Phascolosoma vulgare* de Blainville. 



Sipunculus vulgaris, de Blainville, Diet. d. Sci. Nat., t. xlix., 1827, pp. 312, 313, Vers., 



pi. xxxiii. fig. 3. 

 Sijrinx harveyi, Forbes, A History of British Starfishes, London, 1841, p. 249, with woodcut. 

 Phascolosoma vidgare, Keferstein, Beitrage zur Kenntniss der Gattung Phascolosoma, F. S. 



Leuckart, Zeitschr. f. wiss. Zool., Bd. xii. p. 39, Taf. iii. tig. 3, 1862 ; Ibid., Bd. xv. 



p. 429, Taf. xxxi. fig. 5, 1865. 

 Phascniosnma murgaritaccum, Keferstein, Beitrage zur anatomischen iind sj'stematischen Kenntniss 



der Sipunculiden, Zeitschr. f. wiss. Zool., Bd. xv. p. 530, Taf. xxxi. fig. 9, Taf. xxxii. 



figs. 28, 29, 1865. 



1 F. Vejdovsky, Ueber die Eibildung und Manncben von Bonellia viridis, Eol., Zeitachr. f. u-isn. Zool., Bd. xxx. 

 pp. 487-500, pi. XXX., 1878. 



2 Em. Selenka, Das Manncben d. Bonellia, Zool. Anzeiger, No. C, p. 120, 1878. 



' G. W. Spengel, Beitrage zur Kenntniss der Gephyreen, I. Die Eibildung, die Entwickehing und das Mannchen 

 der BoneUia, Mitteilungen aus der Zoolog. Station %u Neapel, Bd. i. Heft. iii. Taf. viii.-xii., 1879. 



* Strictly speaking the setae are not always absent. In the young larva of Pliascolosoma vulgare, for instance, I 

 found three pairs of setae. These are, however, subsequently thrown off. In the adidt animals true setae seem to be 

 entirely absent. Vide Eifurchung und Larvenbildung von Phascolosoma elongatum, Zeitschr. f. wiss. Zool, Bd. xxv. 

 p. 446, Taf. XXX. fig.s. 14, 15, 18, 1875. 



