AMPHICTENID/E. 35 



no neural canal. The oblique muscles pass by the blunt inner end of the ventral 

 longitudinal muscles and thus are widely separated from the nerve-cords— a rare condition. 



The apparent absence of neural canals in the group is interesting in connection 

 with the supposed special functions of the so-called " giant-fibres." 



Cunningham 1 (1888) describes three pairs of nephridia in Pectinaria belgica, the 

 first the largest, each consisting of a tube bent on itself, and provided with a nephrostome 

 and nephridiopore. The nephrostome of the first is on the anterior side of the septum 

 separating the buccal from the next segment. The others occur on the fifth and 

 sixth segments, the third and fourth being devoid of them. They are brown or black in 

 colour. Between the nephridiopore of the first and the base of the branchia is the 

 aperture of the special glandular organ of the species. The nephrostomes are simple, 

 elongated funnels with the apertures directed forward, and the gonads (undifferentiated 

 cells) are attached to their inner side. 



Linnasus (1767) included Pectinaria along with the Terebellids, the forms he alluded to 

 being P. granulata and P. capensis. Gmelin (1788) somewhat improved on the foregoing 

 by aid of 0. F. Midler's labours in the ' Zoologiae Danicae Prodromus,' and the 'Zoologia 

 Danica' itself. He, however, did not render the position of the Pectinarians and the 

 Terebellids clear, including for instance P. belgica under the genus Sabella. 



Cuvier separated the Amphictenidae from the Terebellae and Sabellae of Miiller, 

 Bruguiere, Gmelin and Lamarck, and constituted the group Ampliitrite, containing not 

 only the Amphictenid se but the Hermellidae. Under this head he enters a protest, so 

 needful in modern times, against the perpetual changing of names, rendering the study 

 of nomenclature much more difficult than that of facts. In Amphitrite the head is 

 furnished with two series of stout bristles having a metallic lustre and resembling combs, 

 whilst above them are the tentacles. The plumose anterior gills do not exceed four. 



The Amphictenidse were relegated by Grube in 1851 to the Terebellif ormia — the 

 practice usually followed up to that date. In 1871 2 he reviewed the characters which 

 linked Terebella, Pectinaria and Amphicteis together, but he followed Malmgren in 

 making each a separate family. He divided the Amphictenea into two groups, the one 

 including Pectinaria, Lam., having two pairs of comb-like branchiae on the third and fourth 

 segments, and Scalis, Grube, whilst Petta had three pairs. The number of bristle-bundles 

 and the lateral processes differ in each. 



This group followed the Hermellida3, and was termed the " Pectinairiens " by De 

 Quatrefages (1865). He regarded these annelids as only partly sedentary, since they 

 can carry their tubes about like those of the Phryganidae. He was at one time inclined 

 to link them on to the Terebellidae, but the disposition of their branchiae and their 

 definite anatomical characters caused him to separate them. Amongst other structural 

 features he mentions that there are two dorsal blood-vessels, and that the chief trunks 

 joining the dorsal with the ventral have pedicled sacculations on each side. He arranged 

 them according to the number of the branchiae, Pectinaria having two and Scalis three 

 pairs. 



Claparede (1868) thought that the separation made by Malmgren between Pectinaria 



1 ' Quart. Journ. Micr. Sci./ N.S., vol. xxviii, p. 254. 



2 < Schles. Gesell./ 6th April, 1870. 



