THE DEVELOPMENT OF SYMBRANCHUS MARMORATUS. 47 
(4) The pronephros is still present in the oldest larva 
examined. 
(5) Mesonephric tnbule-rudiments appear in Stage 29. 
They occur from about Segment 25 to Segment 43. Each 
arises as a rounded clump of darkly stained cells in the 
immediate neighbourhood of the archinephric duct. This 
rudiment is gradually moulded into a twisted tubule, one 
end of which becomes converted into a Malpighian capsule of 
the usual type, the other end acquiring an opening into the 
archinephric duct. 
(6) There are no peritoneal funnels. 
(7) Secondary mesonephric tubules arise in connection 
with the archinephric duct and with the primary mesonephric 
tubules. These are not fully differentiated in the oldest larva 
examined. 
(8) The anterior much-coiled part of the archinephric duct, 
as well as the mesonephros, is surrounded by pseudo- 
lymphatic tissue. 
(d) Vascular System. 
(1) The development of the heart and vascular system 
agrees generally with that described for other Teleosteans. 
(2) The free anterior part of the left posterior cardinal 
disappears, the large right posterior cardinal conveying the 
blood of the inter-renal vein to the heart. 
(3) There is a close connection between the blood-vessels 
of the hinder ends of the kidney and liver recalling the 
posterior vena cava of Polypterus. 
(4) The subintestinal vein, the front end of which is the 
vitelline vein of the earlier stages, persists in the adult as a 
hepatic vein. This hepatic vein joins up with the left 
anterior cardinal and left jugular to form the left ductus 
Cuvieri. The right ductus Cuvieri shows no special 
peculiarity. 
