456 JOHN LEWIS BREMER 



portion of the surface layer. Here again the walls of the cavity 

 are histologically similar to the boundary of the coelom and to 

 the mesothelial cord. In this case the walls are continued in two 

 directions by protoplasmic strands (c and d) broader than the ordi- 

 nary mesenchymal processes, with which they connect, and of the 

 same character as the strand joining the walls of the cavity with 

 surface mesothelium. One of these (c) leads to a second funnel on 

 the surface, and merely proves the coalescence of two separate 

 ingrowths; the other (d) ends blindly, as is shown in the drawing, 

 and indicates either that the distal, as well as the proximal end of 

 the original coelomic diverticulum may be obliterated by fusion, or 

 (which seems to me more probable) that the walls of the divertic- 

 ulum have the power of further growth. In f gure 6 another 

 similar strand is seen at c, which in this section appears isolated, 

 but by reconstruction is found to connect two adjacent cavities. 



The relation between these unlined spaces, which from my draw- 

 ings I can only consider as isolated portions of the coelom, and the 

 angiocysts which have a definite endothelial lining and an extra- 

 intimal space, perhaps due to shrinkage, is indicated in the next 

 two drawings. One, from the body-stalk of Grosser's embryo, 

 (fig. 8) shows the typical mesothelial wall on one side of the 

 cavity, and on the other an apparent delamination of an inner 

 layer, continuous at either end with the mesothelial wall, but 

 separated as a whole by an extra-intimal space from the under- 

 lying layer, which is still an integral part of the surrounding 

 mesenchyma. The other drawing (fg. 9) is from the Minot 

 embryo, near the wall of the coelom at the side of the body-stalk. 

 Two funnel-shaped diverticula from the coelom lead toward the 

 inner cavity, though the mesothelial cords are not so distinct as in 

 the former cases. The wall of the cavity is mesothlelial at the 

 lower left-hand corner, but is continued as an inner lining, with an 

 extra-intimal space. This inner lining, in the form of an extremely 

 thin sheet of tissue containing scattered nuclei, running in part 

 obliquely through the section, in part directly away from the eye 

 of the observer, sends out, in three directions, processes which 

 connect with the inner lining of other similar cavities; one such 



