NO. 4 HARTMAN : POLYCHAETOUS ANNELIDS 397 



abdominal segments is the only means for release of ova and sperm, since 

 nephridial apertures are either absent or restricted to a few anterior seg- 

 ments (see also Eisig, 1887, pp. 794-795). 



Little is known of normal development except for two species, 

 Capitella capitata (Eisig, 1898) and Notomastus latericeus (Wilson, 

 1933). In the first of these the adult exercises brood care until the 

 young larvae swim away. In both species the young pelagic trochophore 

 develops into a typical polytrochal larva and passes through the meta- 

 morphosing, settling stage into a sedentary, limicoline adult. 



Most capitellids are stenohaline, limited more or less strictly to marine 

 habitats. A few are euryhaline; Capitella capitata (Fabricius) and 

 Notomastus (Clistomastus) tenuis, new combination (see below), are 

 common in estuaries and can withstand flooding by rains. Freshwater 

 inhabitants occur rarely, as Eisigella ouanaryensls Gravier from French 

 Guiana. In their known bathymetric ranges capitellids are unique; they 

 occur most commonly in intertidal and littoral zones, especially in mud 

 flats, but their vertical distribution extends through neritic zones to abys- 

 sal depths; the deepest known record is that of Notomastus agassizi 

 (Mcintosh, 1885, p. 389) dredged off New York in 1,340 fms. 



The phylogenetic affinities of the Capitellidae are obscure. System- 

 atically they are generally considered between the Opheliidae and Areni- 

 colidae (Eisig, 1887, p. 891 and Fauvel, 1927, p. 139), but in the struc- 

 ture of the characteristic hooded hooks they are likewise allied to the 

 Maldanidae. There are no known living representatives of capitellids 

 that readily ally them to one or the other of these related families. 

 Inter se they are a distinct group, with a characteristic combination of 

 parts, including the short, plain, prostomial lobe, the eversible, sacklike 

 proboscis, the inflated thorax that is more or less sharply set off from the 

 abdomen, the characteristic parapodia with their unique hooks; additional 

 features include the absence of a closed circulatory system and the almost 

 universal presence of lateral organs. 



Distribution. — The rare occurrence of capitellids in large collec- 

 tions is noteworthy and has been commented on by others (see also 

 Mcintosh, 1885, p. 388). The Challenger Expedition, on its voyage 

 around the world (1871-73), reported 2 species and 2 unidentified frag- 

 ments. Chamberlin (1919a) recorded a fragment from the various 

 collections of the U.S.S. Albatross during four extensive voyages (1884- 

 1909) in various parts of the Pacific and Atlantic Oceans. Ehlers 

 (1887) described one species in the collections of the Blake from the 



