SYLLIDiE. 139 



Eusyllides, the dorsal trunk anteriorly in the ganglionic region splitting into two, which 

 pass anteriorly downward to form the ventral. In each segment, posteriorly, a vascular 

 trunk unites the dorsal with the ventral ; and, in the genital segments, a vascular csecum 

 leaves the ventral vessel a little behind the dissepiment and goes to the genital gland. 



Malaquin describes lymphatic glands along the ventral vessel in certain forms, and 

 amoebicyte-glands in Syllis hamata. The blood is colourless, and the movement is from 

 behind forward in the dorsal vessel ; from before backward in the ventral. 



Some forms are epigamous, others schizogamous or viviparous, and the remarkable 

 condition of several has long given examples of the alternation of generations of various 

 authors. The sexual distinctions between male and female buds, and between these and 

 the nurse-stocks are characteristic. Alternation of generations in Annelids was first 

 suggested by De Quatrefages (1843) for the condition in Syllis monilaris, Savigny, and it 

 was further exemplified by Krohn (1852) in Syllis prolifera. Alex. Agassiz, again, in 

 his account of Autolytus comutus, accurately distinguished the several generations, though 

 he considered the parent-stock to be constantly devoid of sexual elements. It has since 

 been shown 1 that sexual products (chiefly female) appear in segments 11 — 13 of the 

 stock from which the stolon separates, and the same occurs in Procersea ornata and 

 Myrianida. Calvin Mensch, therefore, considers it more a case of sexual dimorphism, 

 and not a sexual alternating with an asexual generation. Epitokous conditions occur in 

 Autolytus longeferiens and in other Syllids. Moreover, some carry eggs in a brood- 

 pouch, whilst others bear them in sacs or in pairs along the body. In no group of 

 animals, indeed, are the complexities of reproduction more pronounced. 



Segmental organs. — E. Horst 2 describes a Syllis-bud with extrusible segmental 

 organs. It has large eyes, like an Alciopid, articulated dorsal cirri, and a brown spot at the 

 base of the foot dorsally, and the terminal pieces of the bristles are bifid. At the ventral 

 base of each foot, except the first, a large dark-brown sac is extruded. JSTo sexual products 

 occurred in the body- cavity. He alludes to the observation of Ehlers 3 that in several 

 species of Glycera, bladder-like bodies (branchiae) capable of extrusion were found. 



Goodrich 4 observes that in young Syllidse the genital funnel can scarcelv be said to 

 exist, being represented only by a few crowded cells in the coelomic epithelium on the 

 anterior face of the septum just above the opening of the small segmental funnel. In 

 budding forms, such as Autolytus, Myrianida, and Haplosyllis, the genital funnel advances 

 little on the foregoing in the regions from which genital products are not extruded. In 

 those shedding the sexual products a large trumpet-shaped genital funnel is formed, as in 

 the Phyllodocidge, on the anterior end of the segmental organ, the dilated canal of which 

 transmits the products. Fage 5 gives similar observations, the minute nephrostome being 

 replaced at maturity by a large genital funnel ; and points out that in the males of certain 

 forms a peculiar transformation of the segmental organ occurs at maturity, a change 

 which he associates with the formation of spermatophores, a kind of sexual dimorphism 



1 E.g. Mensch, 'Americ. Nat./ yol. xxxiy, p. 165 (1900). 



2 ' Notes Leyden Mus./ yol. xi, p. ] 1, pi. i and pi. ii, fig. 1 (1889). 



3 f Die Borstenw./ pp. 659 and 676. 



4 Op. cit., p. 728. 



5 Op. cit, p. 312, fig. 25, and pi. vi, figs. 9—12. 



