108 J. T. CUNNINGHAM. 



considerably larger than the yolk globules, and are seen as 

 empty vacuoles in the protoplasm; they are not very nume- 

 rous, forming an irregular ring, and within them is a pro- 

 toplasmic zone for the most part destitute of yolk globules, and 

 containing the minute vacuoles which probably were occupied 

 by small oil globules in the fresh condition. Here and there, 

 however, scattered yolk globules are seen between the larger 

 oil vacuoles, and in the inner zone of protoplasm. 



I have found that the reason why it is difficult to recognise 

 the smaller oil globules in the prepared sections, is because 

 the oil is entirely dissolved and removed in the process of pre- 

 paration. The reagents used for removing the paraffin from 

 the sections, and for clearing and mounting, namely, benzole 

 or turpentine, necessarily remove the oil originally contained 

 in the eggs themselves. When a portion of an ovary is pre- 

 served with osmic acid, either alone or in combination with 

 other reagents, the oil in the eggs is blackened. I found that 

 some of the blackened oil remained in the sections after the 

 processes of dehydration, soaking in benzole, imbedding, cut- 

 ting, and dissolving the paraffin from the cut sections on the 

 slide, but by the time the sections were mounted with Canada 

 balsam all trace of the blackened oil had disappeared. By 

 washing the sections with alcohol after the paraffin had been 

 removed, and then mounting them in glycerine, a portion of 

 the blackened oil was kept permanently in situ. In order to 

 preserve it completely it would be necessary to cut the sections 

 by an aqueous method, e.g. by the freezing method, and 

 mount them in glycerine, without dehydrating them at any 

 stage. 



The thickness of the zone of yolk spherules continues to 

 increase until it includes the whole of the egg except the 

 germinal vesicle, and a small number of large oil vacuoles, 

 into which the numerous small oil globules of former stages 

 have united. These vacuoles are situated close to the surface 

 of the germinal vesicle. The condition here described is 

 illustrated in fig. 9, which is taken from a preparation made 

 from material preserved at sea on July 22nd in chromic j per 



