138 University of California Publications. [zoology. 



by the original follicle (/.). In this ease the small follicle cells 

 have not disappeared but may be seen packed together in the 

 space around the embryo in the cavity of the follicle {sm.fi. els. ) . 

 Numbers of meseuchymatous cells forming a net work are present 

 in the cavity of the tentacle sheath . 



PI. XIV, Fig. 25, l-epresents a much older stage. This 

 embryo is a compact ball with a well differentiated outer layer. 

 Its greatest length is 150 /*, while the size of the separate cells 

 varies from 5.4 p to about 8 p or 9 ^. At higher mag- 

 nification these larger cells are shown to be in division, but 

 mitosis does not seem to occur more actively in one part of the 

 embryo than another. The absence of the follicle is very notice- 

 able at this stage, but that its loss is probably more gradual than 

 has so far been indicated, is shown by PI. XIV, Fig. 26. This 

 is a section of an ovicell of Crisia oceidentalis, in which the 

 embryo has attained about the development of that in Fig. 25. 

 Here a portion of the original follicle remains in the chain of 

 cells lying below the embryo (ft. els.). These cells occupy the 

 position and have the appearance of the follicle cells of other 

 embryos, possessing the enlarged nuclei with scattered chromatin 

 granules. In this ovicell a number of other cells are present 

 below the embryo which represent a possible source of a second 

 follicle {see. ft. els.). These latter are most numerous in con- 

 nection with a chitinous tube (chi. t.) which extends from a 

 septum (sep.) below the embryo to the base of the ovicell. In 

 development this tube begins as a layer of chitin below the young 

 embryo then consisting of only a few cells. Later the chitinous 

 layer becomes more extensive and assumes a cone shape, the apex 

 of which, with the continued growth of the ovicell, extends to the 

 proximal extremity of the ovicell. Meantime a chitinous ring 

 forms immediately below the embryo (chi. r.), dividing the ovi- 

 cell into two parts. The tissue lining the ovicell is continued 

 over the septum into the tube, and throughout its extent and in 

 close connection with it there appears numerous large cells often 

 possessing two or three nuclei, resembling the giant cells (gi. els.) 

 found in the ovicell of C. ramosa. The interior of the tube is 

 filled with a net-work of deeply staining cells that extends above 

 the septum and around the embryo. The chitinous ring or 



