BrancJiioinaldane vincenti 



151 



portion, which bears fine spinulations. The laminae of the chaeta are 

 not entire at their margin, but are broken up, from the edge inwards, 

 into fine, closely set teeth. The figures represent this part of the 

 chaeta as seen in optical section. In some cases this region of the 

 chaeta appears to be almost enveloped with the fine teeth, and the 

 terminal part is invariably covered with them. In some specimens 

 the two kinds of chaetae tend to merge into one another, and should 

 probably be regarded as different facies of the same type. A noto- 

 podial chaeta of " Clymenides incertus," having a broader distal region 

 and a well-marked constriction near the origin of the lamina on one 

 side, is shown in Fig. 61. 

 Fig. 62 A represents a 

 transitional form, interme- 

 diate between the young 

 chaeta of Fig. 61 and the 

 adult chaeta of Fig. 62 B. 

 The neuropodial 

 crotchets have the same 

 general form as those 



Fig. 63. B. vincenti 

 juv. ("Clymenides 

 incertus "). Neuro- 

 podial crotchet. 



Fig. 64. B. vincenti, 

 adult. Neuropodial 

 crotchet. 



Fi<;. 65. B. vincenti jnv. 

 (" Clymenides incer- 

 tus "). Crotchet from 

 one of the posterior 

 uotopodia. 



of Arenicola, but the tip of the rostrum is very sharp (Fig. 64). The 

 crotchets in each neuropodium are always few in number, they 

 appear never to exceed nine or ten, and there are only two or three 

 in the first two and last segments. 



Prof. Mesnil stated that in his specimens of " Clymenides incertus," 

 which had twenty, twenty-two and twenty-three chaetiferous seg- 

 ments respectively, each of the last six segments bore dorsally a 

 crotchet, either alone or accompanied by a capillary chaeta. One of these 

 crotchets, drawn from one of the original examples of " 0. incertus" 



