228 SPINTHER. 



anterior and the posterior being absent — the result, according to Racovitza, of parasitism. 

 The two ventral nerve-cords are widely separated, with a ganglion in each segment, and 

 a transverse commissure. The alimentary canal has a muscular pharynx without dental 

 armature, with paired diverticula of the middle and hind gut, and a dorsal blind gut. A 

 vascular system is present, but both branchiae and nephridia are absent. The sexes are 

 separate. 



The genus Spinther was established by Dr. George Johnston in 1845 for an Annelid 

 (S. oniscoides) half an inch in length, and fully a quarter of an inch in breadth, which he had 

 received from W. Thompson of Belfast, who had dredged it in six to ten fathoms in the 

 neighbouring bay. It is remarkable that no undoubted example of this species has been 

 found in British waters since that date, though another species has once been procured in 

 the Minch. Dr. Johnston mentions its cream-yellow colour, the absence of distinct " head, 

 tentacula, and tentacular cirri," and gives the number of the dorsal lamellae at thirty. 

 He correctly noticed the general form of the " feet," the presence of the cirrus and other 

 features. He also distinguished the hooks and the various kinds of bristles, though his 

 figures were not drawn with that scientific accuracy — probably from deficient microscopic 

 power — which modern requirements demand. He grouped the genus under the Amphi- 

 nomidae. Unfortunately the type-specimen 1 is not in the British Museum, where Dr. 

 Johnston's collection of Annelids is. The ciliated pits on the anterior portion of the 

 cephalic region are probably sensory (Racovitza). 



Michael Sars five years later (1850) described his Oniscosoma arcticum, n. g. et sp., 

 which he had dredged in Komagfjord, in thirty to forty fathoms, on a sponge. This form 

 had twenty segments, a tentacle and four eyes in the third segment. He gave an 

 account of the dorsal lamellae, the marginal expansions with the bifurcate bristles, 

 and the ventral division with the hooks. He linked it with Euphrosyne. 



Edonard Grube next year (1851), in his ' Familien der Anneliden,' considered that 

 Spinther leaned to the Siphonostomae or to the Amphinomea rather than to the Aphro- 

 ditidae. 



A few years later (1854) Dr. Stimpson formed the genus Gryptonota for a similar 

 Annelid, giving most of the characters already known, and stating further that the 

 branchiae resembled those of Euphrosyne, though he could not satisfactorily make them 

 out. 



Grube (1860), in describing Spinther miniaceus, a new species, placed it near 

 Amphinome. 



In A. de Quatrefages' ' Histoire cles Anneles ' Johnston's species is given at the end 

 of the Ohloremiens, under the genera and species of uncertain position, it being noted 

 that while Johnston considered it near the Aphroditidae, Grube thought it approached the 

 Amphinomaceae and Siphonostomae, and that he (the author) was entirely of the latter 

 opinion, which he based on the structure of the feet, the presence of " albuminous " 

 matter in them, and the nature of the hooks. 



Claparede in a note 3 states that the genera Spinther {Oniscosoma) and Gryptonota are 

 identical. 



1 I am indebted to Prof. Jeffrey Bell for making a search. 



2 { Arch. sc. Phys. et Nat./ t. xxii; 'Bibl. Univ. et Rev. Scientif./ Apr., 1865. 



