FISH IN GENERAL. 97 



passing through this, the roe descends the continuation of the 

 channel, and passes into a bag, situate above the rectum, and 

 constituting a real uterus : this opens by a large orifice 

 at the extremity of the rectum. There is some modification 

 in the structure of the organs of sturgeons ; the egg spawn of 

 rays is fibrous, resembling horn, in form square, flattened, 

 with angles prolonged in points. In sharks the surface is 

 often yellow and transparent, the form oblong, and the angles 

 terminate in long coils of horny cords, which the Baron con- 

 siders as secreted in the lateral furrows of the oviduct, which 

 traverses the gland. The spawn of chimaeras is likewise 

 wrapped in a strong flat shell, of horny substance, oval and 

 hairy ; while that of callorinchus Australis bears a singular 

 resemblance to a broad leaf of sea-weed, within the coats of 

 which the fish, already perfect in form, is discovered suspended 

 in fluid l . 



In viviparous squali, whose embryos are developed in the 

 oviducts or in the uterus, such as true sharks, there is around 

 the foetus only a membranous wrapper, which nevertheless 

 still shows the tortuous cords found about the shell of others. 



Some species of fish carry their egg-spawn upon them after 

 extrusion, and there are others continue the same until the 

 fry is brought forth. Thus syngnathus possesses behind the 

 vent, in the basis of the tail, a groove, closed by two scaly 

 pieces like shutters, wherein the roes remain placed in order 

 until they are hatched ; and it was this particularity which 

 caused Aristotle to assert that this kind of fish split for spawn- 

 ing. Aspredi carry their roes attached to the skin of the 

 belly ; but the greater number of fishes produce the roes in 

 the water, agglutinated by a kind of mucilage which envelopes 

 and attaches them to stones and aquatic plants ; sometimes, 



1 I have received the information relating to callorinchus from Captain 

 King, R.N. C. H. S. 



VOL. x. II 



