1 74 MUNSON. [Vol. XV. 



but they are now separated by clear-cut lines, the less dense, 

 intermediate, lighter layer having apparently been converted 

 into very narrow crevices. In all cases the outer layer, which 

 is the first to originate, differs from the other layers (PI. XIII, 

 Fig. 1 8). 



Both in the living egg and in the preserved material studied 

 in sections the chorion is seen to be traversed by radial stria- 

 tions (PI. XIII, Figs. 12, 17). These are closely set and per- 

 fectly parallel. In the different concentric layers the radial 

 striations coincide as if continuous one with the other. The 

 striations extend even into the outer or first layer of the 

 chorion (PL XIII, Fig. 18). 



The first layer of the chorion arises at the end of the first 

 period, and seems to mark an important epoch in the history 

 of the egg, inasmuch as it is at this time that the cytoplasm 

 loses its affinity for haemato.Kylin, borax-carmine, and other 

 chromatin stains. 



It arises in the form of peripheral bodies, which are scattered 

 at regular intervals over the surface of the egg, immediately 

 under the investing tunic (PI. XV, Figs. 66, 67, "JT, 79, 90). 

 These bodies appear at first as minute dots which increase in 

 size, and stain deeply in chromatin stains. They are often so 

 regularly arranged as to be easily mistaken for nuclei. As 

 they grow, two or three may coalesce, forming a conspicuous 

 body at the periphery of the egg (PI. XV, Fig. 6"]). As they 

 increase in size by coalescence, they gradually lose their affinity 

 for chromatin stains, and eventually all blend into the first 

 layer of the chorion which, when formed, does not stain readily 

 (PI. XIV, Fig. 25, ch). 



This first layer of the chorion sometimes appears to arise 

 as a continuous layer instead of in patches, as described above 

 (PI. XIV, Fig. 20). The first indications of its appearance in 

 such cases are not the peripheral bodies, but a layer of deeply 

 staining dots just under the primary tunic. The granules are 

 not concentrated into larger isolated bodies, but are spread out 

 uniformly. 



The history of the origin of the subsequent layers of the 

 chorion is a different one, although the process in itself may 



