8 F. W. GAMBLP3 AND J. H. ASHWORTH. 



the blue, and lastly the green portions of the spectrum were 

 cut off. 



MacMunn (1889), however, has shown that the alcoholic 

 extract of the integumental pigment shows a band in the blue 

 and green (X 503 — 468) ; that the residue of this solution if 

 dissolved in ether or chloroform yields two bands, X 503 — 474^ 

 and X 465 — 446; and that the residue of this solution again 

 being dissolved in nitric acid gives two bands, X 500 — 468, 

 and X 472 — 443, so that a chlorophan-like lipochrome is 

 present. It is probable that the pigment (melanin) of the 

 skin is derived from the lipochrome of the yellow "glandular" 

 tissue of the stomach, since the alcoholic extract of the latter 

 yields a similar absorption spectrum. 



Further investigation will be required to show in what way 

 the transference of the pigment from the yellow peritoneal 

 cells to the epidermis is brought about, and whether the dark- 

 coloured, hairy-looking investment of the ventral vessel and its 

 branches (PI. 2, fig. 5) contributes to the melanin of the 

 skin. In this connection the intermuscular extension of the 

 ccelom, bringing it almost into contact with the epidermis at 

 certain points, must be borne in mind (see p. 29). 



Setse. — The notopodial setae are long capillary structures 

 averaging 6 mm. in length, and bearing several rows of minute 

 free and pointed hair-like processes (PI. 3, fig. 10). The 

 neuropodia in the anterior somites, which at first contain few 

 setae, gradually extend by addition of new ones at their ventral 

 edge, so as to almost reach the mid-ventral line (PI. 1, fig. 1). 

 By isolating the entire band of the setge the different stages 

 in their development may be seen. The youngest setse are 

 always at the lower end of the series ; the point of each seta 

 is formed first, then the toothed ridge, and lastly the shaft. 

 The fully-developed ventral seta is frequently almost smooth, 

 owing to the wearing down of the teeth behind the apex. 

 The middle of the shaft is straight, the inner end bent ven- 

 trally, and the outer end bent slightly dorsally, ending with a 

 finger-shaped process bordered on the convex side by a toothed 

 ridge, while on the concave side it is slightly produced at one 



