4 MARGARET MORRIS 



The eggs were carried up through xylol to paraffin in the vials 

 in which ihej were preserved, and were kept in the vials while 

 the process of enfiltration took place in the embedding oven. 

 When they were ready for embedding each vial was taken from 

 the oven and held against a cool surface till the paraffin at the 

 bottom of it began to solidify. The rest of the paraffin was then 

 poured off, and the solid mass at the bottom of the vial was 

 picked out with a fine forceps and embedded in a dish of hot 

 paraffin, just as if it were a piece of tissue. As all the eggs settle 

 to the bottom of the vial during the process of enfiltration, the 

 solid mass contains them all and none are lost. If the thing is 

 done quickly so that the mass of paraffin is still very soft, there 

 is no difficulty in getting it out of the vial or in embedding it. 



On account of the large number of eggs cut in a single section 

 it was often difficult to follow one egg through a series of sec- 

 tions. For this reason, large numbers of paramecia were fixed 

 and embedded with the eggs, and their presence served as a 

 guide to the location of an egg in successive sections. Sections 

 were cut 7-9 m. in thickness and stained with iron hematoxylin. 

 Some were counterstained with Orange-G, but this is no im- 

 provement on the plain iron hematoxylin stain. 



III. DEVELOPMENT OF FERTILIZED EGGS 



The maturation and fertihzation of the egg of Cumingia have 

 aheady been described by Jordan. For the sake of convenience, 

 however, it is best to review the phenomena here, especially as 

 the question of the individuality of the chromosomes and the 

 genetic continuity of the centrosomes which were Jordan's main 

 interest are not those which concern us. 



The egg is laid after the first polar spindle has been formed. 

 This spindle (represented in figure 1) is large, and lies near the 

 center of the egg. It might, in fact, be mistaken for a cleavage 

 spindle in the metaphase, if it were not for the form of the 

 chromosomes which is entirely different in the two divisions. 

 If the eggs are not fertilized or subjected to any parthenoge- 

 netic agent they remain in this condition, with the spindle near 

 the middle. After fertilization has taken place, however, the 



