CILETOPODA 301 



cirrus also. The dorsal portion or notopodium, except the 

 cirrus, is wanting. The chief modification in the sexually 

 mature condition is the appearance of the dorsal bundle of 

 bristles, which are very long and serve as natatory organs. 

 The ventral cirrus is absent in one division of the family, 

 the Autolytinae, in which, therefore, the parapodium is most 

 rudimentary. 



The above does not apply to the cephalic segment, and 

 one behind this called the tentacular segment. These two 

 bear no parapodia. 



The appendages of the cephalic segment are five in 

 number : two anteroinferior palps, two lateral antennae, and 

 one median antenna. The tentacular segment bears usually 

 two pairs of tentacular cirri, sometimes only a single pair. 



The forms possessing ventral cirri are divided into three 

 sub -families, according to the freedom or fusion or partial 

 fusion of the cephalic palps. We thus have four sub-families 

 classified as follows : 



f present ( n -, /throughout .... Exogoninse 



Ventral) Palps ' u ^at base only .... Eusyllidinse 



Cirri 1 ( not fused ..... Syllidinae 



(.absent . Autolytinae 



It is necessary to give these characteristics in order to 

 refer to the degrees of asexual multiplication which occur. 



In all the species of the first sub-family, Exogoninse, the 

 sexual reproduction is direct. No fission occurs, the animals 

 present the same phenomena as the Nereidae, that is to say,, the 

 posterior segments become modified when the sexual products 

 are mature, the modification consisting in the development 

 of the bundle of elongated dorsal bristles. The same condition 

 obtains in the Eusyllklinae. In the Syllidinae, however, 

 fission occurs, the posterior modified set of segments separat- 

 ing from the rest, and thus forming a " reproductive zooid." 

 This portion alone produces the ova or spermatozoa. 



