42 KINGS LEY. [Vol. VII. 



being somewhat flattened at first by mutual pressure in the ovi- 

 duct. The average diameter is perhaps two millimetres. Each 

 0.^^ is enveloped in a tough chorion in which a laminated struc- 

 ture is readily recognizable. I have never been able to discover 

 any opening or pores in this chorion through which impregna- 

 tion can be effected, although it is certain that fertilization must 

 take place outside the body of the female, and hence after the 

 chorion is formed. The ^gg proper consists of a large mass of 

 strongly refractive yolk globules of various sizes, and in the &gg 

 as it comes from the oviduct I have been unable to find a trace 

 of a nucleus, nor of nuclear material. No matter what stain 

 was employed, I could not recognize any chromatin granules 

 scattered through or upon the yolk, while anything that might 

 be considered as protoplasm was very scanty. 



In this my experience is paralleled by that of certain other 

 students of Arthropod eggs. The nucleus can be traced to a 

 certain stage of ovarian development where, as Stuhlmann 

 says ('86), " Spater verschwindet das Keimblaschen vor unseren 

 Blicken, bis wir endlich am oberen Eipol der Furchungskern 

 wieder finden." Of course this absence is apparent rather than 

 real, as has been shown by numerous other observations. 



I have been equally unsuccessful in my attempts to witness 

 the phenomena of fertilization, nor have I seen any features 

 undoubtedly characteristic of maturation, although I have sec- 

 tioned many eggs. In one egg, an hour after fertilization, I 

 found on one side a faintly staining structure which I have 

 possibly thought may have been a polar globule (Fig. 3), but the 

 fact that a nuclear stain brought out no chromatin inside the 

 yolk renders this doubtful. 



The various steps of development vary in time, not only with 

 the temperature, but with eggs of the same lot exposed to 

 exactly the same conditions. Hence the ages quoted in the 

 following pages must be understood as averages. Thus, in one 

 lot of eggs I have found phenomena occurring at four hours, 

 which in others occurred at twenty-four hours, while in later 

 stages there may be variations of a month or more. 



At the time of impregnation, the surface of the &gg is covered 

 with dark yolk granules, each granule having a lighter boun- 

 dary. The granules vary in size, and the &gg completely fills 

 the chorion. In fifteen minutes the chorion distends so as to 



