40 BULLETIN OF THE 



deep rose tint, and the transition from the substance of the head to 

 that of the stalk is rather abrupt. It happened that many of the villi 

 from the shell of a mature egg, that was let fall into ninety per cent 

 alcohol without contact with water, and was afterward stained for twelve 

 hours in acetic acid carmine, exhibited a very peculiar appearance at 

 the free surface of their heads. At or very near the middle of this 

 surface the dark border, so characteristic of the heads of the villi, seems 

 to be interrupted, aud there projects from the free end of the head a 

 short conical or longer finger-like process. This issues from the head, 

 apparently through a circumscribed opening in the cortical layer, and 

 may assume a variety of forms, several of which are shown in Plate II. 

 Fig. 2, a-m. This peculiarity is interesting, as showing that there is 

 a region of least resistance in the cortical layer near the apex of each 

 head, which allows the protrusion of a part of the substance of the head 

 when it is subjected to the swelling influence of the acetic acid ; but 

 whether this fact is capable of throwing any light on the source of this 

 villous layer, or the method of its formation, I greatly doubt. 



There is often to be seen in radial sections of the villous layer a 

 strong tendency for the villi to fuse (Plate II. Fig. 2, I). This is 

 especially true of the region of the stalks, although it is also to be 

 observed among the heads. Since this tendency seems to be much 

 greater in some cases than in others, I am induced to believe that it is 

 due to the influence of the reagent with which the egg was hardened, 

 and sometimes perhaps is dependent on the length of time the egg has 

 been in the water before hardening. 



In a few cases — especially in certain nearly mature ovarian eggs 

 which were hardened in chromic acid — I have seen peculiar markings 

 in the villi, which at first led me to think they might be traversed by 

 spaces analogous to the pore-canals of the zona. They were first noticed 

 on tangential sections, and appeared there like minute circular holes in 

 the segments of the prismatic villi (Plate II. Figs. 4, 5). Focusing 

 showed that their contents were much less refractive than the substance 

 of the villi, and they were consequently very sharply defined. But the 

 notion that they were optical sections of tubes, like pore-canals, was at 

 once corrected upon finding isolated villi, which had fallen out of the 

 layer and were seen sidewise. When the thickness of the section is 

 about equal to the diameter of the villi, it is difficult, if not impossible, 

 to decide whether the isolated angular blocks are seen endwise or side- 

 wise ; but by selecting the thicker sections, where the length of thf 

 villous segments is greater than their diameter, the difficulty is avoided 



