192 PROCEEDINGS: BOSTON SOCIETY NATURAL HISTORY. 
epithelium is relatively thin, being thickest Avhere the nuclei are 
lodged, and attenuated between the more or less widely separated 
nuclei, thus imparting a peculiar appearance to the sections, which is 
unlike what we observe in the pronephros of the gill-less urodela 
and anura, in which the epithelium has the nuclei closer together 
and the cells distinctly cuboidal in type. Opposite the nephrostome 
Fig. 3. Necturus maculatus ; larva of 18.0 mm. Transverse section thronlig 
the pronephros. Harvard Embryological Collection, No. 16, section 341. Ao , 
aorta; Glo , glomus ; Ec, ectoderm ; t, t, tubules ; Si, sinusoid ; msth , meso- 
thelium ; Coe , coelom ; Nst, nephrostome. 
is a large glomus, Glo, the base of which lies close to the aorta, Ao ; 
the glomus apjiarently contains a network of capillaries. The great 
size of the cells in Necturus will be appreciated if figure 3, which is 
magnified only 100 diameters, be compared with the other figures, 
which are, with two exceptions, all magnified 300 diameters. In 
brief, the pronephros of Necturus shows the same type of sinusoid 
circulation as is well known in other Amphibia, but it has a number 
of distinctive histological features. Since the character of the circu¬ 
lation in the amphibian pronephros has been well described and 
figured by Max Ftirbringer, ’78.1, A. Goette, ’75.1, H. H. Field, 
91.1, and R. Semon, ’91.1, it seems superfluous to dwell upon it. 
