372 TRANSACTIONS LIVERPOOL BIOLOGICAL SOCIETY. 



been stated, composed of a solid mass of cells, all of which 

 seem to have equal chances of developing into mature ova. 

 In many cases, however, development only continues in 

 those cells around the periphery of the ovary. The 

 central cells do not develop any further, but gradually 

 lose their individuality, the cell membranes disappear, 

 and the nuclei are absorbed. These changes in the central 

 cells result in the formation of a central, non-nucleated, 

 cytoplasmic core surrounded by developing oocytes. It is 

 interesting to notice that these oocytes are distinctly pear- 

 shaped : the narrower part of the cell being embedded in 

 the central mass, while the nucleus is lodged in the broad 

 part of the cell (PI. Y, fig. 26, oc). Certain of .these 

 cells develop much more rapidly than the others, and 

 increase so much in size that they protrude considerably 

 beyond the surface of the ovary, and are only enclosed by 

 a fine membrane composed of a single layer of much- 

 flattened cells. It is very easy to conceive of these oocytes 

 being dislodged from the ovary, and this is what actually 

 does happen, for when they have reached a certain size 

 they are transferred to the egg sac, while still immature, 

 and here they complete their growth. 



In the course of my investigations of the living 

 worm, I have several times succeeded in teasing out and 

 freeing from the body the ovary, in a more or less complete 

 condition. In most cases, its appearance very nearly 

 resembles that seen in sections, and although the oocytes 

 in this condition are very transparent, it is possible, by 

 the addition of a little methylene blue, to stain them 

 sufficiently to examine them before disintegration sets in, 

 which, by the way, takes place very rapidly. As a rule, 

 there is no special blood supply to the ovaries. It has 

 already been mentioned that the perivisceral vessels of 

 segments 10, 11 and 12 are much enlarged in the mature 



