478 F. W. GAMBLE AND J. H. ASHWORTH. 



II, CEsophageal Connectives. 



In the "marina" section of Are nicola the connectives are 

 slender. They spring from the ventro-lateral angles of the 

 anterior lobes of the brain, which at this level are widely 

 separated by a coelomic space. In the ecaudata section, 

 however, the brain is so short and broad that it passes almost 

 insensibly at its outer ends into the connectives. 



The farther course of the connectives is marked externally 

 by the "metastomial" grooves. In A. marina these grooves 

 are sometimes quite distinct, especially in living specimens, 

 in others they are faint and sometimes invisible. In A. 

 Claparedii they attain their maximum development (PI. 27, 

 fig. 62), and may be traced as oblique grooves on the body, 

 commencing on each side at the nuchal organ, where they are 

 deepest. They unite in the mid-ventral line on the third 

 annulus. In A. cristata they are absent, while they are 

 rather faintly indicated in A. ecaudata and Grubii. 



The connectives lie just to the inner side of the epidermis 

 lining these grooves, and they unite in front of the first 

 chsetigerous annulus. The exact position of their point of 

 union — the beginning of the ventral cord — occurs just an- 

 terior to the annulus in front of the first parapodium. 



In the post-larval stages of A. marina the union of the 

 connectives occurs in an annulus, dorsally possessing the 

 vestigial chffita seen by Benham, and belonging to the first 

 segment following the peristomium. Counting the peri- 

 stomium as a segment, this would place the origin of the cord 

 in the second segment, one annulus in front of the first 

 chaetigerous segment of the adult; and the same applies to A. 

 Claparedii. In A. cristata the union of the connectives 

 occurs even further forwards. At first they are slender, and 

 arise from the anterior end of the brain, which is here not 

 distinctly lobed, though distinctly subdivided into right and 

 left portions. From this point they run almost vertically 

 downwards and slightly outwards, but do not lie close to the 

 epidermis. 



