DEVELOPMENT OF PARACOPIDOSOMOPSIS 33 



in figure 72 is eleven days old, and only a few masses, on the 

 left, are beginning to break away. In stages still older one may 

 find a considerable portion of the polygerm, at the original seat 

 of infection, still intact. 



d. Origin and history of the sexual embryos 



The multiplication of the embryoic masses, from the primary 

 stage to the formation of the tertiary components, is a continuous 

 process. As already stated, the distribution of the tertiary 

 masses and their components to various parts of the caterpillar 

 follows the dissociation of the polygerm. The components thus 

 distributed became the centers for the formation of groups of 

 sexual embryos, either directly or after further multiplication, 

 depending upon the stage at which the scattering occurs. Since 

 one cannot follow the history of a single tertiary component, 

 it is not easy to determine at just what point multiplication of 

 components ceases and embryo formation begins. However, 

 one can meet this difficulty by studying stages fifteen or sixteen 

 days old with well-developed sexual embryos, and tracing their 

 origin back through a series of younger stages. 



As the multiplication of embryonic masses progresses the num- 

 ber of embryonic cells included in each mass naturally becomes 

 smaller and smaller. This occurs notwithstanding the fact 

 that the embryonic cells are also multiplying, because the rate 

 of division of the embryonic cells does not keep pace with the 

 increase in number of the embryonic masses. 



In the tertiary divisions, and more particularly in those of 

 the components, it is not uncommon for a single embryonic 

 cell to be separated out into an embryonic mass (figs. 63, 65). 

 The method of division in the tertiary masses is sHghtly different 

 from that found in the case of primary and secondary masses. 

 Both in the primary and in the secondary masses the division 

 is effected by a simple constriction of the inner membrane (figs. 

 60, 62). In the case of tertiary divisions there first grows in 

 from the inner membrane a number of protoplasmic processes 

 which divide the embryonic cells into several groups, each con- 



