562 EMBEYOLOGY OF THE LOWEE VEETEBEATES OH. 



Berlin Aquarium it has been observed that pairs of eggs were deposited 

 at intervals of about ten days. The methods of technique mentioned 

 in connexion with the Skate are also applicable to the eggs of 

 Scyllium. "- 



It should not be forgotten that, as mentioned earlier in this 



V7TT W 



"V, \ \ i v.cN. 



ot. 



UcV 



Fig. 248. — Raia batis, embryos. 



at, atrial portion of heart ; E, eye ; c, eonus ; f.g, foregut ; H, heart ; I, lens ; li, liver ; ot, otocyst ; 

 pin, pineal organ ; r/i, thin roof of fourth ventricle ; v.c.l, etc., visceral clefts ; y.s, yolk-stalk ; V VII 

 VIII, cranial nerves. 



volume, one of the greatest desiderata in Vertebrate embryology is 

 an oviparous shark with eggs of small size. 



Teleostomi. — The most archaic and therefore the morphologically 

 most important surviving member of this group is- Polypterus and 

 strenuous efforts have been made to obtain .developmental material. 

 Harrington lost his life on an expedition to the Nile with- this object. 

 Budgett made two expeditions to the Gambia, one to Nigeria and 



