420 



C. H. DANFORTH 



absent from the first arch in the adult. The present writer finds 

 them occuring invariably in all the arches. 



The efferent arteries, with the partial exception of the fourth, to 

 be described presently, parallel very nearly the afferent vessels as 

 indicated in figure 7. They arise ventrally by two long branches, 

 one from each hemibranch, which unite at about the same level 

 as that at which the recurrent afferent artery is given off. This 

 corresponds very well with what Silvester ('04) found to be the 



m. lev. > 



a. bi 



a. nu. c. ep. i 



m. obv. 1 



c. cer. 1 



a. br. a. 1 



a. br. e. 1 



Fig. 7 Anterior aspect of the first gill after the removal of some of the super- 

 ficial tissues. 



condit'on in a large number of teleosts. Dorsally the efferent 

 vessels all send off small branches to accompany the terminal 

 bifurcations of the afferent arteries. Throughout the whole 

 gill the efferent fi'amentar arteries tend to unite in tree-like 

 groups (cf. fig. 9), a single stem often draining several filaments. 

 Morphologically the dorsal and ventral branches may be simply 

 enlarged stems of this sort that have developed with the increased 

 size of the gill. If such be the case they probably do not indicate 

 an incomplete fusion of a pair of efferent vessels such as occurs 



