3)6 PROCEEDINGS OF THE ACADEMY OF [May, 



posteriorly. On somite XII there are no ventral and only 1 to 3 

 dorsal setae. 



Anteriorly the color is a delicate pink which resides in the ovaries, 

 testes and oesophagus ; this is purest as far back as the setae of somite 

 VI and again in XI and XII, but is elsewhere obscured by the brown 

 color of the chlorogogue cells. In the yovmgest worms the blood is 

 colorless, in larger ones sulphur yellow, and in still larger ones reddish- 

 yellow. At all ages these worms are transparent and especially so 

 when young, rendering the anatomical study of living ones an easy 

 matter. 



The septa -y, yj and yjj are thickened and jy only less so. The 

 three most anterior bear large, clear septal or pharyngeal glands, the 

 third being more granular than the others. The brain (fig. 24) is 

 slightly longer than broad, straight or slightly truncate anteriorly, with 

 the prostomial nerves and circumoesophageal connectives arising from 

 the antero-lateral angles; jvist behind these is the narrowest part, 

 from which the width gradually increases to the two quadrate posterior 

 lobes, which are separated by a moderate cleft and give rise to a pair 

 of muscle strands. Copulatory supra-neural glands are well developed, 

 especially in somites III, IV and V. They are slender and elongated, 

 not closely united with the ventral nerve, and open on each side nearly 

 at the ventral setae bundles. 



The blood vascular system presents the usual simple structure found 

 in species of this genus. There is a well-developed periintestinal sinus 

 terminating anteriorly at VII. The dorsal vessel is conspicuous and 

 contractile for most of its length, becomes free from the intestine in 

 XIII, and terminates without bifurcating at the anterior margin of 

 the brain, where it joins the pair of vessels arising from the two loops 

 into which the ventral trunk splits in III. Ccelomic corpuscles (fig. 

 25) are of two kinds, much the most numerous being elongated, irreg- 

 ular, flattened, colorless and finely granular ones measuring about .025 

 mm. long and .008 mm. wide. The other and less numerous being 

 flattened, irregularly circular disks, with large granules and a pale 

 grayish-green color, which are .015 mm. in diameter. 



Nephridia of the form shown in fig. 26 occur regularlj^ in pairs in 

 every somite, except XI, XII and XIII, from VII caudally. They 

 have very small funnels and massive tapering postseptal regions, from 

 the postero-ventral angle of which the large efferent duct, which is 

 shorter than the massive portion, arises and passes to the external 

 pore. 



When fully developed the testes, which occupy the usual position in 



