142 University of California Publications. izoology. 



tissue, is yellow. Perhaps the most interesting sight is the 

 primary embryo which floats out with the rest of the material 

 and frequently beeomes isolated. It may easily be obtained by 

 the dissection of a living ovicell, or from a stained decalcified 

 ovicell dissected in a drop of oil. In the latter case the embryo 

 is a more compact and clearly defined mass than in the former, 

 but the characteristic features of both are the same. Projecting 

 from the surface in various directions protuberances appear 

 which are the buds of the secondary embryos. 



Near the top of the ovicell represented in Fig. 28, the primary 

 embryo appears much reduced in size, but still budding actively. 

 As budding continues the primary embryo decreases in size, both 

 as a whole, and in the size of its individual cells. This may be 

 seen by comparing Pigs. 27 and 31, the latter representing 

 the primary embryo of Fig. 28 drawn to the same scale as 

 that in Fig. 27. This, as has been said, measures 200 ^ in 

 length, while the older embryo (Fig. 31), measures but 71 /* in 

 length. In the older embryo cell boundaries are less distinct, 

 and the cells are more closely massed together. In examining a 

 number of ovicells, primary embryos are frequently found much 

 smaller than this, and much smaller than the contained larvae. 

 Thus in one instance the primary embryo measures 50 p and the 

 adult larva? 86 p. This ovicell contained a number of secondary 

 embryos 25 /* in diameter. The secondary embryos in the older 

 ovicells average slightly smaller than those in the younger. It 

 seems extremely probable for several reasons that the primary 

 embryo is completely used up in the process of budding. Evi- 

 dence for this is found in the gradual decrease in size of the 

 embryo resulting from its continued activity in budding. Again, 

 the instance of Crisia occidentalis (Fig. 29) in which the primary 

 embryo divides into a large number of secondary and tertiary 

 embryos, so that no one of the masses present can be called the 

 primary embryo, and in which each mass of cells is apparently 

 either redividing or is transforming into a larva, is strong evidence 

 that no portion of the original embryo is left over. Further, 

 complete series of sections of ovicells are obtained in which no 

 primary embryo can be found, although larva 3 and half grown, 

 secondary embryos are abundant, and the aperture of the ovicell 



