UKALFISIIES. 



311 



e(|ual to tluit of tlie l)o(l)-. Tlic ;il)(l<iiiiiii;il p;irt of the; 

 body y;/«,s' the head is al)out eciual in huij^th to the <'aud;d 

 part, hut the base of the ventral tins still remains just 

 behind and l)el()w that of th(! pectoral. IA)ui- of tiie rays 

 in eaeh ventral fin are already elongated. The caudal tin 

 lias be<jun to form the first rudiments of its true rays 

 below the end of the notochord, which is curved up- 

 wards at the tip, though as yet oidy slightly. Extei-- 

 nally, however, the tip of the tail is still symmetrical, 

 with a lobate extensioti of the (Mnbr\onie verticsd tin 



itself (jii the skin. In other respects the lai'va is only 

 slightly changed from the appearance it had at a length 

 of 9 mm.; but the development of the embryonic pec- 

 toral lins is now arrested, theii' l)i-acliiatc base showing 

 signs of reduction. The five occi])ital I'ays of the doi'sal 

 fin and the three outer \(Mitral rays have attained a 

 length more than douI)le that of the body, but are 

 united to a fairly great extent at the base by the tin- 

 nunubrane. Tlu; three iinier rays of the ventral tins 

 graduallv diminish in length. The vent lies at the end 



Fig. 78. Yoiiug specimen of Trachijptevus iris, 10 mm. in lengtli. After Emery. 



Fig. 79. Caiiiliil liii nf a Traclii/plerns iris 2l5 mm, long, from Messinn. r/, embryonic vertical tin rpf the back; 

 V, embryonic vertical tin of tlie ventral edge; c/i, chorda dorsalis. 



which is about eiiually large above tind below the end 

 of the notochord; Imt onh' the lower lolje is furnished 

 with rudimentary rays, while in the upper we find only 

 the priinarv fibrilLe, which are destined .soon to dis- 

 appear, together with the whole of this lobe. Chro- 

 matophores are scattered both on the raised occiput 

 and the sides of the abdominal cavity. 



In the next stage of the development described by 

 IvMEiiV (fig. 78), the larva has attained a length of 16 

 mm. The silvery colour has now begun to deposit 



of the second third of the length of the body. The 

 embryonic vei'tical tin is still present along the ventral 

 margin, but there are no rudiments of true ravs in front 

 of the caudal tin, .ind there seems to be no rudiment 

 of a true anal tin. The caudal fin, on the other litiiid, 

 has passed through a great ])art of its early alterations. 

 This fin originates, here as in all Teleosts, at the 

 ventral part of the caudal end of the eml)ryonic (larval) 

 vertical fin, but in front of the end of the notochord. 

 It thus belongs originally to the .same division as the 



