Katharine Foot and E. C. Strobell 20.1 



ill a very small drop of water on tlie slide, the membrane is carefully 

 pricked with a very fine needle and as the cytoplasm flows out, the egg 

 membrane is gently dragged away with the needle, allowing the contents 

 of the egg to spread and dry immediately. By this method the germinal 

 vesicle, and sometimes even the spindle, flow out of the egg membrane 

 intact, and dry so quickly that the structures are remarkably well pre- 

 served. The vesicle when drying flattens out over a larger area, leaving 

 the individual chromosomes or threads sufficiently separated to be 

 clearly identified, and when the entire spindle passes out of the egg 

 membrane intact, all the eleven chromosomes are beautifully demonstrated 

 on one plane. In this manner we arrange from 20 to 30 eggs on a slide, 

 which has been previously ruled with a diamond into definite areas, so 

 that the position of each egg is known and any egg can be studied later 

 in connection with data taken before it was killed.' 



Cytoplasm. — During the development of the egg when the prophases 

 of the first maturation spindle occur there is a marked change in the 

 structure of the cytoplasm and during this period there is a decrease in 

 the size of the egg and an increase in the amount of the substance between 

 the egg membrane and the outer membrane, greatly increasing the width 

 of the letter area. Compare the space between the two membranes 

 shown in Photos. 13, Plate I, and 68, Plate lY, eggs at the germinal 

 vesicle stage, and that of Photos. 99 and 100, Plate Yl, where the first 

 maturation spindle is at the metaphase.^ We have demonstrated these 

 two membranes in earlier papers (1897, Fig. 2) (1901, Photos. 57 and 

 59), and shown that AUolohophora possesses in common with many 

 OUgochcetes, a delicate outer membrane and an equally delicate membrane 

 in contact with the egg itself, the space between the two being filled with a 

 relatively non-stainable substance. Yejdovsky and Mrazek have observed 

 these two membranes with coagulated substance between them in many 

 Lumhricidce and they criticise Gathy's interpretation of the three layers 

 in Tuhifex as one thick membrane. 



The difference of size and densitv between the eo-g-s at the terminal 

 vesicle stage and those containing the first maturation spindle is very 

 evident in living eggs, the latter being smaller, more dense and more 

 opaque and these features are equally evident in the dried preparations. 

 At the germinal vesicle stage the typical cytoplasm shows a distinct 



' Such slides do not resemble smear preparations, they suggest rather slides 

 with a few thick sections far removed from one another. 



* This contrast is really more marked than shown in the photographs, as 

 Photos. 13 and 68 are magnified nearly 300 diameters more than Photo. 99. 



