146 SYLLIILE. 



objection can be taken. Benham, again, makes the family the first of thirteen under his 

 sub-order Nereidiformia, and thus links them to such divergent forms as the Aphroditidge, 

 TomopteridaB, Nephthydidaa, Amphinomidge, Grlyceridas, Sphasrodoridas, Arieiidas, and 

 Typhloscolecidas. It is true that Levinsen, under the second group of his Syllidiforma, 

 viz. the S. spionina, associates the Spionida3 3 Chastopteridaa, Cirratulidas, Ariciidse, 

 Chlora3mida3 (?), and Ophelida3 (?), but this is all that can be said in its favour — after 

 substituting Nereidiformia for Syllidiformia. 



Pruvot distinguished two forms only in the Syllides, viz. Pseudocephale (Chastosyllis, 

 Tetraglena, S. arnica) and Uucejphale (Ioida). 



In the Pseudocephale the oculiferous lobes are separated from the cerebral ganglia. 

 In the Uucephale the lobes are fused and contain the cerebral ganglia. 



In Benham's 1 classification this is the first family of the sub-order Nereidiformia of 

 the Branch Phanerocephala, though upon what principal is uncertain. It is followed by 

 such as the Hesionidas, Aphroditidaa, Phyllodocidas, Tomopteridaa, and Nephthydidse, a 

 classification which appears to be at variance with natural affinities and with structure, as, 

 indeed, Miss Florence Buchanan has ably pointed out. It has been considered better to 

 follow the arrangement given by Malmgren and others than to adopt this classification, 

 wdiich, however, in its primary branches, viz. Phanerocephala and Cryptocephala, certainly 

 gives expression to actual facts. 



Calvin Mensch 2 finds that in certain parent-stocks of Autolytus ornatus, Verrill, after 

 the separation of buds at the fourteenth segment, sexual elements appear in the eleventh, 

 twelfth, and thirteenth segments, and he suggests the possibility of the parent-stock 

 developing into a sexual form subsequently, though he has not observed the changes in 

 the eyes, bristles, and other parts — probably because the examples were too young. This 

 may be a case similar to Haswell's. 



Hacker 3 (1896) figures a metatrochophore of Syllis with two eyes, three separate 

 tufts of cilia on the sides, and a paratroch. Gland-cells occur on the ventral aspect, and 

 the alimentary canal is simple and cylindrical. He gives a later stage, in which only a 

 protrotroch and a paratroch remain, whilst the long space between them has fifteen 

 segments, the head is more elongated (conical), and the eyes are at the posterior border. 

 A large black pigment-speck is present. Each segment has a pair of hook-like bristles. 



In a note, in 1902, on the British Syllidae, 4 the increase in the number of genera 

 and species was alluded to. 



Perhaps the most natural grouping of the Syllidse is that of those authors who 

 arrange them primarily into (1) those with palpi fused but prominent (Exogonea), 

 (2) those with palpi separate (Syllidea proper, Langerhans), and (3) those with the palpi 

 fused (Autolytea). These groups are readily subdivided by the condition of the pharynx, 

 the nature and number of the tentacles and tentacular cirri, the condition of the head and 

 first segment, and especially the structure of the feet and bristles. Moreover, a fourth 

 group, the Eusyllidea (Malaquin), in which the palpi are fused at the base only, may be 



1 f Camb. Nat. Hist./ vol. ii, p. 306 (1896). 

 3 ' Zool. Anzeiger/ June 15th, 1896. 



3 "Pelagische Poly chat enlarven/' ' Zeitsch. f. w. Zool./ Bd. Ixh, p. 82, Taf. iii, figs. 6 and 7. 



4 Mcintosh, < Ann. Nat. Hist./ ser. 7, vol. ix, p. 296. 



