DEVELOPMENT AND LIFE-HISTORIES OF TELEOSTEAN FISHES. 787 
it is interesting to see a large glandular structure, such as the so-called head-kidney, 
which may be made out in early embryos, and which is from the first closely associated 
with the main hemal vessels of the trunk. The lymphatic system, with its plasma and 
leucocytes, is really intermediate between a venous and an arterial system, and is 
associated with the various serous membranes, pleural, peritoneal, pericardial, and others. 
It is not surprising that large lymphatic masses should occur so near the centre of the 
blood-system, and though BaLrour was not inclined to regard them as parts of the 
true kidney at all, they cannot at any rate be regarded solely as degenerate pronephric 
structures. WELDON, in his brief but interesting paper on Bdellostoma (No. 156), 
suggests that such masses are represented in all vertebrates by the suprarenal bodies. 
In Bdellostoma the archinephric or segmental duct is separated from this anterior mass, 
though in some specimens, possibly younger, traces of the continuity of the two could be 
made out. In embryonic Teleosteans the continuity is very patent, and in the adult 
condition renal tubules still ramify amongst the lymphatic tissue, as BaLFour found in 
Esox, Lophius, and Osmerus. In the last species a single tubule alone passes into the 
vascular lymphatic mass. It would appear, indeed, as if the embryonic pronephros in the 
process of degeneration were usurped by the antenephric lymphatic structures, the 
proximity of both favouring this, while the persistence of stray tubules in the posterior 
part indicates the pronephric portion. GROosGLIK’s researches upon various adult 
Teleosteans (Cyprinus carpio, Esox lucius, Rhodeus amarus, Gastrosteus aculeatus) con- 
firm BaLrour’s view, as he found coexisting in the region of the head-kidney lymphatic 
tissue and remains of the atrophied pronephros surrounded to some extent by the cardinal 
vein, while some pronephric tubules still pierced the lymphatic meshwork (No. 60, 
pp. 605-611). Emery, however, maintains that the pronephros persists permanently in 
such as Fierasfer and Zowrces; while in other forms, as Blennius, it is provided with 
glomeruli and tubules, and in Merlucius esculentus it presents the peculiar structure of 
the Wolffian body. In all it persists as a recognisable pronephros (No. 53a), a view which 
Hyrtt held; while Raruxe and Sranntus concluded that in Cyprinus the head-kidney 
is degenerate, and bereft of tubules, a view now generally adopted. The segmental duct 
precedes the development of the Wolffian body, and cannot therefore be a mesonephric 
duct, as BaLrour suggests (No. 11, p. 701); it is in fact a pronephrie duct, or more 
truly it is archinephric, for the pronephros is secondarily developed as a convoluted 
anterior portion. It is possible that this duct may not represent the primitive condition, 
but rather a segmental canal bereft of its serial segmental tubules and nephrostomes, 
save the single infundibulum at its anterior termination.* The view generally accepted 
however, is that which interprets it as a primitive non-metameric renal duct. The ducts 
retain their simple tubular character in the adult condition, and pass along the latero- 
ventral margins of the fully-developed renal masses. In the last larval stages, within a 
* The fact, however, that some segmental tubes, consisting of nephrostome, capsule, and convolutions, develop in 
Elasmobranchs independently of the duct, and later connect by their originally blind end, may indicate that the serial 
condition is secondary. It illustrates at any rate their separation and independent coexistence, whatever the explana- 
tion may be. 
