238 



Annelida Ghcetopoda 



finger shaped, extending a little beyond the feet. Ventral 

 cirri swollen at base, outer third suddenly attenuated. 



Setge, in two bundles. Upper bundle made up of two or 

 three compound setae, appendix short, bidentate (f. 76), 

 and one simple seta (f. 77), long, acute, with a narrow bor- 

 der ; one straight black acicula (f. 79). Lower bundle, 

 two or three of the compound bidentate setae ; one com- 

 pound seta (f. 78), with a long, narrow, acute appendix; 

 one bidentate acicula (f. 80). 



(6.) In the next stage there is a slight depression of the 

 anterior margin of the head, one antenna, as in f. 81; the 

 bidentate setae have disappeared from two or three of the 

 anterior segments, the other forms (figs. 77,78) are more 

 numerous. In other respects same as {a). Length, 2.5-4™™. 



(c.) As a next step, the anterior emargination becomes a 

 little deeper, and a shallow median depression extending 

 back a short distance, above and below (f. 81), indicates 

 more clearly than before the future division of the head 

 into palpi. Simple finger-shaped branchiae appear on the 

 10th setigerous segment. On a specimen with 36 setigerous 

 segments there are 13 pairs of branchiae; of these the first 

 two, and the last three, are shorter than the others. 



Length, 4""°^. 



[d.) In the next form, there are three antennae. In one 

 specimen the lateral antennae are mere buds (f. 82). Eyes 

 four to two. The median eye disappears first, next one or 

 both of the anterior eye specks, so that on specimens other- 

 wise the same there may be two, three, or four eyes. The 

 division of the head into palpi becomes better marked. The 

 shape of the feet becomes somewhat changed ; the bidentate 

 setae gradually disappear from the anterior segments, un- 

 til on the largest of the series they are found only on the 

 posterior third ; a second straight acicula is added to the 

 upper bundle of setae, and a second bidentate acicula to 



