4 Reticulated Basement Membranes in the Submaxillary Gland 
forming the organ, while probably not exceeding divisions of the first 
and second orders, consists of solid columns of cells lying in a rather 
dense syncytial connective tissue, from which they are sharply differ- 
entiated. The syncytium is not yet completely separated into exoplasm 
and endoplasm, to use Mall’s terms for the fibrillar and cytoplasmic 
portions of the embryonic framework of the organ. Immediately sur- 
rounding the tubes is a dense blue staining line which has the same 
reaction as the exoplasm, while just outside of this, and, indeed, resting 
directly upon it, is a mass of branching and anastomosing syncytial cells 
which form, with the other cellular elements of the syncytium, a direct 
protoplasmic continuum. Still further external a somewhat clearer 
differentiation of the developing connec- 
tive tissue into exoplasm and endoplasm 
is obtained. Short, branching anastomos- 
ing fibrils of varying caliber are seen 
scattered here and there in the syncytium; 
this exoplasm in many places appears as 
dots which represent often simply fibrils cut 
in cross-section. At a great many points 
exoplasmic fibrils extend from the surround- 
ing tissues to the basement membrane and 
here and there one sees deeply-staining 
fibrils apparently in the endoplasm of the 
cells immediately surrounding the cell col- 
umns. Now, whether the basement mem- 
branes up to this point are formed solely 
fan dillaey ee boneseen ccanowaie by the deposition of fibrils or whether the 
he developing basement mem- : 1: Sei : a 
Fie auar the Rajacent eyuay: synevtial protoplasm differentiates into exo- 
tium. Exoplasm just differen- RePe Cs) i Zs . Te 
tiatine from the embryonic plasmic structures just about the develop- 
y tive tissue. Pig 3 cm. : sre se ; 
Fixed in Zenker’s fluid. Mag. ing glandular cells, it is very difficult to sav. 
ified 900 diameters. ao 
ai? WES CEN IT but in all probability the basement mem- 
branes in the early stages are formed in both ways, namely, by a pri- 
mary deposition of exoplasm from the syncytium and later augmented 
by increments of millions of fibrils from the general syncytial exoplasm. 
Following the formation of the membranes beneath the epithelium of 
the buccal cavity or in the skin in these preparations does not throw 
definite light on this question for in a pig 3 cm. in length the mem- 
branes when viewed tangentially appear to be made up partly of exo- 
plasmic fibrils and partly of a simple granular substance in the meshes. 
The problem is complicated by the fact that in the earlier embryos, the 
endoplasm is diffusely tinged by the blue element of the dye. This 
