MINOT : SINUSOIDAL CIRCULATION. 
193 
In Amniota the pronephros, so far as known, is never developed 
into a functional organ, but seems rather to persist merely to give 
rise to the pronephric duct, and accordingly it never acquires a 
proper circulation of its own. 
Conclusion. The blood circulation of the pronephros is sinu¬ 
soidal in marsipobranchs , ganoids , teleosts , and amphibians , and 
there is no exception known. 
2. Mesonephros or Wolffian body. I have shown in my 
previous paper, ’98.1, that the intertubular circulation of the middle 
or second kidney is sinusoidal in mammals, birds and Amphibia. 
I wish to use the present opportunity to publish certain further 
considerations and observations, and a drawing to show the condi¬ 
tion in the chick. 
As regards the mesonephros of fishes we possess little informa¬ 
tion as to whether the circulation is sinusoidal or not. That it is 
sinusoidal is a priori probable from our knowledge of the conditions 
in Amphibia and Amniota. The very intimate relations of the 
cardinal veins to the renal organs have of course been long known. 
Thus Hyrtl ( Denkschr . Wien. Akad ., 2, 1851, p. 34) in his paper 
on the kidney of teleosts writes, “ Sehr oft bilden die Nierenvenen 
Sinuse, indem sie sich spindelformig oder spharisch erweitern und 
mehr weniger innig mit dem umgebenden Nierenparenchym ver- 
wachsen, jedoeh nie so innig, dass sie nicht aus demselben ohne 
Verletzung ihrer Continuitat herausgezogen werden konnten.” He 
gives no information as to the vessels within the kidneys. Nor 
have I succeeded in finding the desired record of observations in 
any of the authorities whom I have been able to consult. The only 
new observations I can offer concern elasmobranchs. In embryos 
of Acanthias up to the length of 34.0 mm. the mesonephros is a 
series of segmental tubules more or less completely imbedded in 
mesenchyma, with the intertubular circulation scarcely developed 
at all. One may compare Rabl, ’96.2, Taf. XVII, fig. 12, a sec¬ 
tion through the 25th mesonephric segment of a female Pristiurus 
of 30 mm., the oldest stage described by Rabl in his very valuable 
and careful monograph. In this and other stages near to this stage 
the cardinal vein lies above the base of the «;enital fold on the 
median side and quite close to the coils of the segmental organ, 
compare Fig. 133, p. 236, in my “ Human Embryology.” The 
blood vessels about the tubules are figured by Rabl as being near 
the epithelium only, not in contact with it. In three Acanthias 
