SUB-ORDERS 305 



SUB-ORDER 4. The Capitelliformia have no prostomial pro- 

 cesses, but possess a pair of large retractile " ciliated organs." The 

 parapodia do not project; the chaetae are unjointed, and are 

 hair-like in the anterior segments and hooded " crotchets " 

 posteriorly; this external division of the body does not corre- 

 spond with definite internal differences. There are no cirri, though 

 special " gills," often retractile, are frequently present. The buccal 

 region is eversible ; there is no armed pharynx. An " accessory 

 gut " or " siphon " exists. The nephridia are small, and sometimes 

 more than one pair in a segment ; special genital funnels exist 

 in more or fewer of the anterior segments of the hind body. 

 There is no system of blood-vessels ; the coelomic corpuscles are 

 red. The worms are burrowers. 



SUB -ORDER 5. The Scoleciformia possess a prostomium, 

 which rarely (Chlorhaemidae) carries any sensory processes ; the 

 peristomiurn is without cirri (except, perhaps, in the Chlorhae- 

 midae). The parapodia are ill developed, and may be absent ; 

 only rarely are dorsal cirri present, acting as gills ; ventral cirri 

 are absent. The chaetae are unjointed ; true uncini are not 

 present. The buccal region is eversible, but there is no armed 

 pharynx. The septa are not regularly developed, as more or 

 fewer are absent, and the nephridia are considerably reduced in 

 number, it may be to a single pair (Sternaspidae and some 

 Chlorhaemidae), but they are all alike. 1 The worms are mostly 

 burrowers. 



The branch CRYPTOCEPHALA contains two sub-Orders : 



SUB-ORDER 1. Sdbelliformia. The prostomium is entirely 

 hidden by the forward extension of the peristomium ; the ten- 

 tacles are very small, being frequently represented merely by 

 small knobs of sense-cells; the palps, on the other hand, are 

 greatly developed, branched, and contain blood-vessels, acting as 

 respiratory as well as sensory organs. The peristomium never 

 carries cirri or chaetae, and it is usually raised up into a pro- 

 jecting collar, used in fashioning the lip of the animal's tube. 

 The parapodia are but feebly developed ; cirri are absent, except 

 in the Serpulidae, where the dorsal and ventral cirri become united 

 to form the " thoracic membrane " (Meyer). The chaetae are 

 of two kinds unjointed, hair-like, fringed bristles and " uncini." 



1 It is probable that the genital ducts of Sternaspis and Chlorhaemids are modified 

 nephridia. 



VOL. II X 



