1 34 MUNSON. [Vol. XV. 



toneal coat being conspicuous by the distinct nuclei of its 

 cells, while in the second coat, or tunica propria, no nuclei can 

 be seen (PI. XIV, Figs. 33-41. t.p.). 



Comparing the tube with its tunica propria, with the walls 

 of the enclosing lymph spaces, it is seen to differ from these 

 in this, that while in the latter the body of the cells is 

 greatly flattened (PL XIV, Figs. 37-41, p.c), so that the 

 nucleus finally seems imbedded in the outer lamella, in the for- 

 mer the body of the cell remains conspicuous, and the nuclei 

 are accordingly considerably removed from the common invest- 

 ing membrane, the tunica propria. In the peritoneal cells the 

 intercellular or cementing substance is formed between the 

 cells, which thus become adherent at their circumference; 

 while in the germ cells this intercellular substance appears at 

 the outer pole of the cell, which thus retains more of its 

 spherical form. 



In some of the tubes of an embryo seven inches long, 

 traces of muscle cells can be seen between these two coats ; 

 and this is, of course, the future muscle coat of the ovarian 

 tube. As the animal increases in size the muscle coat 

 becomes more and more pronounced. 



Even in an embryo five inches long it can be seen that some 

 of the germ cells have passed the period of multiplication, and 

 have entered on the period of growth (PI. XIV, Fig. 38). As 

 they grow they push their way out, causing a separation of 

 the peritoneal membrane and the tunica propria on either side 

 (PL XIV, Figs. 40, 41, /.f., t.p), and this circumstance seems 

 to determine the position of the follicular fenestrae of the 

 muscle coat (PL XIII, Fig. 15, m.c, t.p). It might be asked 

 whether the increased pressure thus produced between the 

 egg and the peritoneal membrane, and the resulting diminution 

 of pressure on the other side of the egg, has anything to do 

 with the peculiar arrangement of the muscle fibers. It will 

 be seen later that these oocytes make their appearance at 

 regular intervals as the animal grows ; and that this is inti- 

 mately connected with the increasing diameter of the ovarian 

 tube. But the further account relating to this will be intro- 

 duced with the history of the growing egg. 



