SPINTHEB. 229 



Malmgren in his ' Aimulata Polychseta ' (1867) included Sars's species under the 

 genus Spinther — as 8. arcticus, Sars. 



In 1865 I found in the Minch, off North Uist, a form which was placed under 8. 

 oniscoides, Johnst., but which is clearly S. miniaceus, Grube, or more correctly 8. arcticus, 

 Sars (non Wiren). 



Hansen next (1882) describes a form which he identified with 8. arcticus, Sars, from 

 the Norske JSTordhavs-Expedition. The description and figures, however, as von Graff 

 says, agree better with S. oniscoides, though the somewhat indifferent drawings of the 

 bristles leave some doubt. 



In the account of the Annelids of the Yega Expedition (1883) Wiren described a 

 species which he calls 8. arcticus, but which materially differed from Sars's form in size 

 and in structure. 



The same year Levinsen, in his systematic account of the geographical distribution 

 of the northern Annelids, confused Sars's species with Wiren's, and made Hansen's 

 (8. oniscoides) a new species. 



Drasche 1 further in 1885 gave an excellent anatomical description of S. miniaceus, 

 Grube. He found this species chiefly on the surface of the sponge Tedania anhelans, 

 Lieberk., at Trieste. He pointed out the double nature of the dorsal membranes — of 

 the structure of which he gives good figures. Underneath the cuticle is the hypoderm, 

 which is thickened in certain regions. The muscular investment which occurs next is 

 more or less continuous as an outer longitudinal and an inner circular layer, but in his 

 figure (pi. ii, fig. 7) of the ventral region the reverse arrangement is shown. His 

 description and figures of the cephalic ganglia (brain) are good, as are also his remarks on 

 the eyes. He gives a clear account of the alimentary canal and of the dorsal blind gut, 

 which joins the intestine in front of the rectum. His account of the circulatory system is 

 brief, since he had only examined the system in section — a dorsal vessel, a ventral trunk, 

 and transverse vessels in each segment being the chief features alluded to. He concludes 

 his paper with remarks on the body-cavity and its septa. Between each pair of septa are 

 the ganglia of the ventral cords and their commissure, the diverticula of the gut and the 

 transverse blood-vessels. The rest of the cavity, in his specimens, was filled with the 

 reproductive products. In the male the region of the dorsal blood-vessel is specially 

 connected with the development of the sperms, as Haswell and Selenka showed in the 

 Aphroditacea. He found no segmental organ (nephridium). 



The most complete account of the genus, however, is that of L. von Graff (1887). 

 This author had an extensive series of specimens, and brought to bear on their structure 

 modern methods of investigation. After an historical introduction he gives the characters 

 of the genus and the three species known, viz. 8. oniscoides, Johnston, 8. miniaceus, Grube, 

 and 8. arcticus, Wiren. The adoption of the specific term arcticus for the latter, however, 

 seems to be open to some objections, since Sars's name arcticus has some claim to priority 

 over Grube's term miniaceus, and confusion may result from the application of the same 

 name to a different species, northern though it be. He shows that 8. miniaceus is the 

 smallest of the series, 8. oniscoides considerably larger (26 mm.), while 8. arcticus 



1 Drasche, R. von, ' Beitrage z. feniereu Anat. der Polychasta/ Wien, 1885, 14 pp., 2 pis. 



