138 U.S. NATIONAL MUSEUM BULLETIN 227 



subequal antennae. Tentacular cirri 1-3 pairs. Body divided into 

 2-3 regions: anterior region with prenatatory unmodified setigers 

 without swimming setae; middle region with natatory setigers in which 

 the parapodia become more elongate, with long swimming setae de- 

 veloped in newly formed notopodia; and posterior region of un- 

 modified setigers without swimming setae (the latter region may be 

 nearly lacking). Neurosetae as in the stem form. Dorsal cirri rather 

 long, subequal. Large yolky eggs found within the body or 

 enclosed in a 1- to 3-lobed, delicate but durable, transparent ventral 

 brood sac, the body of the female being coiled ventrally around 

 it. The larvae pass through their early stages within the sac, develop- 

 ing 2 prominent anterior and posterior ciliated bands. 



IS'Iale stolons or polybostrichus stage (figs. 37, a-b; 40c) : Diflfer from 

 the female stolons in that they have a pair of short frontal antennae, 

 a very large median antenna, a pair of large forked palps, the inner 

 fork usually thicker and curled. Tentacular cirri 2-3 pairs; usually 1 

 pair of tentacular cirri are very long and coiled, similar to the median 

 antenna (in A. alexandri, the first pair of dorsal cirri are modified in 

 this way). Body divided into 2-3 regions as in the female stolons; 

 testes and sperm in prenatatory segments. 



Key to the New England Species of Autolytus 



1. Neurosetae simple, with bulbous tips, with or without hairlike tips (fig. 37c). 



Male and female stolons with 6 prenatatory setigers, 2 pairs tentacular 



cirri. (Known from .sexual stolons only) A. eniertoni 



Neurosetae compound, with stem inflated distally, with appendages short, 

 curved, bidentate (fig. 38e), and a single upper simple bayonette seta (at 

 least in posterior segments; fig. 38rf) 2 



2. Stem form with dorsal cirri short, subequal, about half the length of the 



body width (except anterior two pairs) ; sexual stolons produced singly, 

 with head of stolon forming between setigers 13 and 14 (rarely between 

 12 and 13 or 14 and 15), the body of the stem form posterior to setiger 13 

 (12-14) developing into the sexual stolon (fig. 38a). Sexual stolons with 

 6 prenatatory setigers, 3 pairs of tentacular cirri and a pair of small 

 achaetous knobs; in male stolon, first pair tentacular cirri similar to dorsal 

 cirri with second pair at its ventral base, third pair very long and stout, 

 similar to median antenna, with small achaetous knob at its ventral base 

 (fig. 37, a-h); in female stolon, similar except both the first and third pairs 



are similar to the following dorsal cirri (fig. 39) 3 



Stem form with dorsal cirri longer, more than half the length of the body 

 width; sexual buds formed at least posterior to segment 19 4 



3. Body with 3 longitudinal light to dark black bands middorsal and dorsolateral 



at the level of the bases of the dorsal cirri (fig. 37J) ... A. prisniaticus 

 Body with reddish brown transverse dorsal bands, 1 per segment, on every 



segment or at irregular intervals (fig. 38a) A. fasciatus 



Body colorless or with faint dusky dorsolateral longitudinal bands (fig. 37e). 



A..cornutus 



