SYLLIDS. 145 



of the antennae, the development of swimming-bristles, the development of the genital 

 glands in the median and posterior regions of the body, and changes in the segmental 

 organs. They are parallel to the changes seen in Nereis. 



In a subsequent paper 1 he demonstrates that epigamy occurs in the family just 

 mentioned (Nereids), in the Syllids, particularly in Exogone and Eusyllis, and in the 

 Hesionidse, e. g., Kefersteinia cirrata. Further, that schizogamy is present in the Syllids 

 and occasionally in the Capitellidae, and in this a part of the individual only acquires 

 sexual characters and is separated. In the Syllids schizogamy has various forms, viz. : 

 (1) Acephalous, ex. Syllis (Haplo syllis) hamata, Clap. ; (2) Tetraglene, ex. Try jpano syllis ; 

 (3) Ghsetosyllis, ex. Syllis prolifera, Krohn ; (4) Syllis arnica, De Quatrefages ; (5) Ioida, 

 ex. Syllis (Typosyllis) hyalina, Gr. In Autolytus the form assumed is that of Sacconereis 

 for the female, and Polybostrichus for the male. 



He points out that at the period of maturity the eyes of the Syllids having direct 

 reproduction enlarge, and become lateral in position, or move to the ventral surface. In 

 the pelagic sexual forms the great development of the eyes is a necessary accompaniment. 

 An additional pair of pigment-specks is occasionally seen in front of these two pairs, but 

 they are not true eyes. 



He shows that in the group of the Syllides (Malaquin) as contrasted with the Autolyti, 

 the sexual forms resemble each other, even to the distribution of the male and female 

 sexual glands. Again, they differ from the Autolyti in the variation in different types. That 

 variation exists not only in distinct genera, but in closely allied species in the same genera. 



Malaquin describes the small segmental organs as having the ciliated funnel projecting 

 anteriorly from the septum, and with a long, narrow canal, which opens on the ventral 

 surface by an extremely minute pore. 



He gives an account of several larval stages of Syllis hyalina frequenting Polyzoa, 

 and indicates how the development runs parallel with that of Eusyllis, only the formation 

 of the proboscis is more rapid. His earliest stage had two setigerous segments, and the 

 larval pharynx was comparatively long. The intestine opened by an anus. The larva 

 with five bristled segments had the proventriculus behind the pharynx, and the rounded 

 palps projecting from the sides of the head. When the larva has seven or eight setigerous 

 segments the structure is much the same as in the adult. 



In Syllis, Grubea, and Exogone the ciliated apparatus of the larva disappears and the 

 phenomena are abridged. 



Bisig's 2 opinion that the lateral cseca of the alimentary canal in the Syllids performs 

 the function of swim-bladders does not meet with much support, especially as such a 

 provision is not distinctive of highly pelagic types — types in which, for instance, swimming- 

 bristles are developed on specially modified feet. The bodies of these animals are so 

 plastic at the reproductive season that the modifications of an organ designed to aid in 

 distributing the sexual elements could not fail to have attracted notice, and to have more 

 or less differentiated pelagic from non-pelagic types in this alone. 



The SyllidaB form one of the families under the group Syllidiformia vera of Levinsen 

 (1883), and are placed between the Hesionidse and ISTerillidse, a position to which no great 



1 'Zool. Anzeiger/ No. 514 (October 5th, 1896). 



2 'Mitth. Zool. Stat. Neap./ ii, p. 255 (1881). 



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