Nr. 9] 



CONTHIB. TO THK LIKK HISTORY OF l'HK PISHES 



27 



The head has a hook-shaped projection at Ihe base of which, 

 indication-s of the eye may be observed, as an oval prolube 

 rance with a smaller oval in the centre. Towards the point of 

 the hook the first indication of the olfaclory organ is apparent 

 as a small furrow. The mouth forms an équilateral Lriangle, 

 with the apex pointing backwards. Behind the eye there are 6 

 fissures, of which the first, long and narrow, forms the first 

 indication of the spiraculnm. The remaining 5 are gill slits. At 

 the fore edge of the 4 first gill- slits there are 2 small knobs, 

 the commencement of the provisory gill threads. Similar gill 

 thread knobs are also developed later in the oth gill slit, but 

 not in the spiracnlum. Indication of digestive tract quite distinct. 

 As in the case of the teleostian fishes, there is a dorsal and a 

 ventral embryonal fin, Ihe dorsal running from the 3rd or 4lh 

 gill slit to the point of the tail, while the ventral extends from 

 the anus to point of tail. The anterior portion of the dorsal 



Fig. 7. Embryo of Raja vadiqta from Gulosen, l l-2 1910. Capsule 2. L. "28 mm. 



embryonal fin is very small. The umbilical cord is allached a 

 little behind the oth gill slit. There is no distinct indication of 

 dorsal lins at this stage of development, but the peclorals are 

 seen commencing as a narrow strip along the side, e\tending 

 from the anterior end of the umbilical cord lo a little way back. 

 Behind the pectorals, and in the same plane, is a longish ridge 

 forming the commencement of the ventral lins. The segmenta 

 tion in the chorda dorsalis is distinctly visible. 



The next stage which I have been able lo procure is that 

 in a capsule from Gulosen, V2 1910, caps. 2. The total length 

 of the embryo here was 23 mm. (fig. 7). 



The head, viewed laterally, is still hook-shaped. The devel 

 opment of the gill threads is farther advanced, the foremost 

 having now the appearance of short threads, while the hinder 

 ones are more like knobs (pl. I fig. 2). The pecloral lins have 

 grown out forward to the oth gill slit, and the flaps of the 



