140 MUNSON. [Vol. XV. 



In the adult the relation of the egg to the ovary and of the 

 various parts of the ovary to one another is essentially the same 

 as in the younger forms (PI. XIII, Fig. 15). As compared 

 with the younger forms the ovarian tubes, in cross section, are 

 greatly enlarged, and the number of diverticula, in cross sec- 

 tion, are proportionately increased. But this is not necessa- 

 rily true of the number of eggs that may appear in cross 

 section, for after the discharge of the first set of eggs into the 

 ovarian tubes a number of empty pouches containing no eggs 

 may be seen (PI. XIII, Fig. 15). These occupy the same posi- 

 tion which the discharged egg previously occupied. Originally 

 they arise, as has been seen, in the young animal by the push- 

 ing out of the tunica propria through the fenestrae of the 

 muscle coat as the egg grows. The sister cells of the egg 

 after division of the oogonia become the lining cells of the 

 stalk of the egg. The stalk of the egg, however, exists only 

 during the empty state of the tube, for when the tube becomes 

 stretched by mature eggs that have been discharged into it, 

 the stalk of the egg disappears and its epithelium constitutes 

 the lining epithelium of the ovarian tube. 



While it is true that throughout the various stages of growth 

 of the animal the number of eggs in cross section of a tube 

 regularly increases, there appears to be a period beyond which 

 no new eggs are formed. In an animal eighteen inches long 

 eight eggs appear in a cross section of a tube. Several animals, 

 among them a soft-shelled one, equaling in size some of the 

 females that were observed ovipositing at Woods Holl, had 

 discharged no eggs from the follicles, and yet the number of 

 eggs in cross sections had not increased. 



Notwithstanding a most careful examination of ovaries from a 

 large number of adult females, collected both at Woods Holl 

 and at New Haven, and showing empty follicles, having evi- 

 dently reached the period of sexual maturity, I have in no case 

 been able to observe the first stages of the forming egg as it is 

 so easily done in the earlier stages of the growing animal. I 

 infer, therefore, that new eggs are not formed after a certain 

 period, and that this period is either earlier than the period of 

 the first discharge of the oldest egg into the ovarian tube or 



