40 



Arenicolidae 



mens of A. ecaudata. I also found crotchets * in the posterior 

 notopodia of a post-larval A. ecaudata, 8 mm. in length. This 



X 150 



Fig. 5. A. ecaudata. Outline of the posterior end of a post-larval specimen, 8 mm. long, to 



show the chaetae. 



specimen has recently been subjected to further 

 clearing, and this has rendered it possible to get 

 a better view of the dorsal crotchets, which are 

 not as short as they are drawn in the figure cited. 

 Fig. 5 is a more accurate representation of this 

 specimen and of its two types of crotchets, which 

 are shown more highly magnified in Figs. 6, 28 

 (p. 56). Elongate crotchets, similar to that of 

 Fig. 6, are present in the last five notopodia of 

 post-larval examples of A. branchialis, 4*4 and 

 5 * 8 mm. long respectively. 



I have examined a series of larval and post- 

 larval A. cristata for notopodial crotchets, which 

 are already present in larvae with four or five 

 chaetiferous segments. A larva, 7 mm. long, with 

 ten chaetiferous segments (Fig. 7), bears in each 

 of the last six notopodia a crotchet of the long 

 type. In an older specimen, 2 6 mm. long, which 

 has the full number (seventeen) of chaetiferous 

 segments, only one notopodium, the penultimate, 

 contains a crotchet ; and in a specimen 3 mm. 

 long crotchets are not present in any of the notopodia. 



It is clear from these observations that a crotchet, differing from 



1 Figured in Q. J. Micr. Sci., xliii (1900), pi. xxiv, fig. 37. 



F1 i 



.-A. ecaudata. 



