368 J. T. PATTERSON. 



peripheral layer of smaller cells. Surrounding the mass is a 

 thin envelope formed from the trabeculse of the nucleated mem- 

 brane. The large central cells are clearly the embryonic cells 

 proper. 



The multiplication of secondary masses to produce other masses 

 continues for a long period, at the close of which the final products 

 of division develop into embryos. However, during the course 

 of development, usually early in the period of multiplication, 

 the polygerm fragments or dissociates, the secondary masses 

 becoming widely scattered throughout the body cavity of the 

 caterpillar. The point at which dissociation takes place varies 

 greatly in different cases. It may occur at the close of the third 

 day, or it may be delayed until as late as the tenth or eleventh 

 day. Indeed, in some cases, the polygerm does not completely 

 dissociate until the larvae are ready to be set free in the body 

 cavity of the host. Apparently, the dissociation is in part 

 controlled by the relation of the polygerm to the host tissues. 

 If the polygerm lies free in the body cavity, or in loose tissue, 

 dissociation will occur very early; but if it is imbedded in fat or 

 other dense tissue, the dispersal of the secondary masses may 

 be greatly delayed. 



The polygerm on the left of Fig. 9, although only seventy- 

 seven hours old, has already begun to fragment. Several second- 

 ary masses lie some distance from the main body of the polygerm. 

 Two of these appear in the photograph. The polygerm seen in 

 Fig. 13 is ninety-five hours old, and lies free in the body cavity. 

 Dissociation is well advanced, and secondary masses are widely 

 dispersed. In addition to the secondary masses, it has formed 

 four asexual embryos at as many different points. The polygerm 

 in Fig. ii is eleven days old. It was dissected from the fat 

 tissue of the host. It contains a large number of secondary 

 masses, some of which are beginning to break loose from the 

 main mass, and two conspicuous asexual embryos. These fe\\ 

 cases will serve to show the variation in the time at which dis- 

 sociation begins. 



V. DEVELOPMENT AND FATE OF THE ASEXUAL LARVAE. 



While some polygerms produce asexual embryos at a very 

 early stage (Figs. 3, 4, 5, 9, 13), nevertheless the majority of such 



