The life history of Dipiocliscus temporatus Stafford. 619 



attachment to the outer layers of the wall through a more or less 

 attenuated strand of cytoplasm. 



The earlier stages in the formation of the egg cells are shown 

 at the edges of the ovary in the cytoplasmic layer on either side 

 of the sporocyst. At these points, where the thickness of the cyto- 

 plasmic layer is intermediate between that of the ovary and that 

 of the opposite pole of the sporocyst, there is taking place the 

 formation of definite cells, by the ingrowing of cell walls which 

 isolate a single nucleus with a definite amount of cystoplasm. At 

 first these walls usually extend entirely through the cytoplasmic 

 layer so that the resulting cell is roughly cuboid in shape. The 

 distal end (next to the body cavity) soon becomes rounded and 

 shrinks away from the inner wall of the sporocyst so that the 

 resulting cell has the shape of a half ellipse. Further inward, 

 toward the deepest part of the ovary, the cells become narrower at 

 their bases and consequently higher. 



In the stage shown in Fig. 12 the process of localisation has 

 gone further. ]\Iost of the nuclei in the cytoplasmic layer are now 

 contained in that end of the sporocyst where the cytoplasmic layer 

 is the thickest. Some fully formed cells-(eggs) one of which has 

 already given off its polar bod}^, are being set free from the ovary 

 into the body cavity; which contains embryos in two quite distinct 

 stages of development. 



In the fully developed sporocyst the ovary has the appearance 

 which is shown in Fig. 13. Here the cytoplasmic layer about the 

 greater part of the body cavity is very thin and contains only a 

 few scattered nuclei. The ovary, on the other hand, is proportio- 

 nately very deep. It is made up of cells each of which has its 

 nucleus at the distal end. The oldest, tallest, cells reach nearly to 

 the surface of the ovary and retain their connection with the inner 

 layer of the body wall through a very thin strand of cytoplasm. 

 In the interstices between the bases of the taller cells there are 

 other cells which extend only a short distance from the muscular 

 layers of the body wall. These last mentioned cells are attached 

 by comparatively broad bases so that they are nearly hemispherical 

 in shape. They undoubtedly represent earlier stages in the deve- 

 lopment of the eggs, comparable to those found at the borders of 

 the ovary in the stage represented in Fig. 11. 



The figure given by Haswell (1903) of the ovary of Echinosto- 

 mum sp. is very similar so that found in Dipiocliscus iemporatus^ 



