292 A. E. Verrill — Nem England Annelida. 



1862. — Alexander Agassiz. On Alternate Generation in Anne- 

 lids^ and the Einhryology of Autolytus cornvtus.<^Joicrnal 

 Boston Society of Natural History., Vol. vii, [^jp. 392-409, 

 2)1. 9-11], Jrdy, 1862. 



Antolytus cornntus, s}). iiov., p. 390, pi. 9-11. Massachusetts Bay, 

 Buzzard's Bay. 



Autolytus longosetosus A. Ag., p. 404, [21], Male=?A. longisetosus ; 

 female probably=A. Alexandri Mgu, Massachusetts Bay. 



Mr. Agassiz states that the form that he supposed to be the female 

 of A, longisetosus has "no less than ten" anterior segments, without 

 long setae. Among the numerous specimens of Autolytus collected 

 at Salem, Mass., by Mr. J. H. Emerton, there are both males and 

 females of what I consider the true A. longisetosus (pi, 12, figs. 10, 

 lOa, 10c, S •) These have, m both sexes, six short anterior segtnents, 

 lacking long dorsal seta;, and bearing only short ventral seta?; the 

 post-buccal segment bears very long dorsal cirri (dc), but no seta?. 



In the same lots, collected in early spring, there is a very distinct 

 species, Avhich has, in both sexes, fourteen anterior segments, with 

 short ventral seta? only, including the first post-buccal segment, which 

 bears a pair of very large dorsal cirri, and a small cluster of seta? 

 directly beneath them ; the second segment is also very much com- 

 pressed, and its seta? are more or less completely concealed by the 

 large cirri, in a dorsal view (plate 12, figs. 8-8c). These are, perhaps, 

 the A. Alexandri Mgn., and they may prove to be the sexual forms 

 of my Stephanosyllis ornata. If so, it would confirm the separation 

 of StepJumosyllis, as a genus distinct from Autolytus. 



In the sexual forms that I consider identical with Autolytus cormi- 

 tus A. Ag., I have constantly found six anterior setigerous segments in 

 both sexes (pi. 12, fig. 4, $ ; fig. 6 $ , ventral views), but in the male 

 the first fascicle is concealed, in a dorsal view, by the large dorsal 

 cirrus of the first post-buccal segment; this first segment bears no 

 sette, in this and the several allied species, wliich I consider typical 

 Autolyti {\>\. 12, figs. 5, 6, 9-9^, 10, 10«), but in this species it has 

 a small papilliform ventral cirrus, not mentioned by Mr. Agassiz. 

 He also failed to notice the ventral tentacular cirrus of the female, 

 though he figures and describes the corresponding cirrus of the male. 

 Although this organ is small, and often seen with difficulty, especially 

 when the body is much compressed, as repiesented in the figures by 

 Mr. Agassiz, it is quite as large as in the male, and often projects 

 beyond the sides of the head. 



