456 



There are two external membranes, the chorion and the vitelline 

 membrane. The chorion is made up of two membranes : an outer, 

 or exochorion, and an inner, or endochorion. It is difficult to dis- 

 tinguish these two layers in sections, but sometimes when the eggs 

 are removed from the fixing agent to 70% alcohol the inner layer 

 separates from the outer one in bubble-like areas, and the two can 

 then be further separated by needles. The vitelline membrane is 

 somewhat thinner and much more delicate than the chorion. The 

 former stains more heavily with hsematoxylin, while the latter stains 

 more heavily with orange G. I was not able to distinguish any 

 structure that I could identify positively as a micropyle. Ganin 

 (1869) states that there is a single micropyle at the posterior end of 

 the egg. Blochmann (1884) states that a micropyle occurs at the 

 animal pole or upper end of the egg. It is probable that he means 

 by "animal pole" the posterior end of the egg, since he says that he 

 found what he took to be the egg nucleus and the sperm nucleus at 

 that end of the almost ripe o\^rian egg. In the freshly laid egg the 

 nuclei always occur at the posterior end. 



If a freshly laid egg be sectioned longitudinally, it will be found 

 to present the appearance shown in Plate I, Fig. i. On the outside 

 is the chorion, which stains rather deeply with orange G; and inside 

 the chorion, closely investing the protoplasm, is the vitelline mem- 

 brane, which takes the hzematoxylin stain. On the inside of the 

 vitelline membrane is a comparatively thick layer of peripheral pro- 

 toplasm, much thicker at the posterior than at the anterior end or 

 at the sides. The part of this layer in the posterior one-third of the 

 egg is noticeably different from that of the anterior two-thirds, that 

 at the anterior end being much more vacuolated, with a tendency 

 toward network formation, while that at the posterior end is almost 

 devoid of vacuoles. Numerous small yolk granules are seen embedded 

 in this protoplasmic layer, especially at the posterior end. In many 

 places the small granules are found fitting into small pocket-like de- 

 pressions. In other places the outer edges of these depressions, meet- 

 ing, enclose the granules in vacuoles. This indicates the manner in 

 which the yolk granules probably become embedded in the peripheral 

 layer of protoplasm. 



Another respect in which the protoplasmic layer at the posterior 

 end differs from that at the anterior end and at the sides is in the 

 presence of an immense number of minute rod-like bodies which al- 

 most completely fill the protoplasm at that end of the egg and stain 

 readily with hsematoxylin. Blochmann ('84, pp. 245-246) mentions 

 finding these bodies in the ovarian eggs of Camponotus ligniperdis 



