100 TEBEBELLKLE. 



separates the branchial segments from the succeeding and thus the respiratory chamber is 

 free from the contents of the coelom. 



The vessels on the alimentary canal send jets into the dorsal and also into the sub- 

 oesophageal plexus which communicates with the vessels of the collar. From the latter 

 arise the vessels which carry blood to the branchiae. The trunk conveying oxygenated 

 blood joins the ventral. There are heart-bodies in Terebella flexuosa and T. multisetosa. 

 In Terebella MecJcelii he found two folds in the intestine like a typhlosole. The reduction 

 of the cerebral ganglia to a simple transverse commissure without trace of division occurs 

 in Terebella flexuosa. ' In Terebellids he asserts that tubular fibres in the nervous system 

 are absent, yet in T. flexuosa a homogeneous substance resembling the contents of the 

 tubular fibres is seen on each side of the middle line (Plate X, fig. 1), as in Audouinia 

 filigera. In Terebella Meclcelii the nerve-cords are in the circular coat in Claparede's 

 figure, since fibres are outside them, but in the text he observes that they are hypo- 

 dermic. In Terebella flexuosa the cords are so united in the thorax that the halves are 

 indistinguishable. He thinks, therefore, it is an exaggeration to say that the Annelids 

 have a double nerve-cord and the Gephyreans a single one. 



Ray Lankester 1 (1873) detected hemoglobin in the blood of Terebella. 



Grube (1878) in. his ' Philippine Annelids,' gave a description of the genus Terebella, 

 L., s. str. Sav., in which, whilst furnishing nothing new, he puts the characters in an 

 orderly manner. He adds that segment 1 is bare, and the next, 3 or 2, rarely 1, 

 branchiferous. The branchiae are three pairs, two pairs, or rarely one pair, ramose, 

 arborescent, or now and then bifurcate at the base or in the form of cirri. 



Cosmovici (1880) furnishes a general description of the structure of the Terebellidae, 

 especially in connection with the segmental organs and organs of Bojanus, a term applied 

 to the glandular part of the segmental organs. His description of the parts is confusing. 



The Terebellidae formed the first family in Levinsen's (1883) group Terebelliformia, 

 the others being the Ampharetida3 and Amphictenidae. Perhaps little advantage is 

 to be gained by such grouping other than Malmgren obtained by placing them seriatim 

 in his series. He arranges the genera as follows : Lysilla, Amoea, Leucariste, Terebellides, 

 Artacama, Thelepus, Amphitrite, Pista, Lanice, Terebella, Nicolea, Axionice, Scione, 

 Trichobranchus, Streblosoma, Grymoea, Thelepodopsis, Laphaniella, Leoena and Laphania. 



Marenzeller (1884), in an important discussion in connection with the Adriatic forms, 

 states that in the Terebellidas the following holds in the arrangement of the rows of hooks : 

 I. Hooks alternate, uniserial — Pista cristata, P. cretacea, Nicolea venastula, 

 Polymnia nesidensis. 

 II. Hooks opposite, biserial — Amphitrite gracilis, Leprdea lapidaria. 



III. Hooks turned inwards {inverse), biserial — Lanice conchilega and Loimia. 



Between I and II. 



IV. Hooks semi-opposite, incompletely biserial — Amphitrite cirrata, A. variabilis, 



A. rubra, Polymnia nebulosa. 

 Between I and III. 

 Hooks semi-inverted (inversi), imperfectly biserial. 



Moreover, he placed under the genus Nicolea both Scione and Axionice, 

 1 l Proc. Roy. Soc./ No. 140, 1873, p. 3. 



