DEVELOPMENT OF PARACOPIDOSOMOPSIS 37 



standing in the way of the full acceptance of this hypothesis, 

 there is the further objection that it does not explain the absence 

 of organs other than those of reproduction, nor does it take into 

 account the fact, established by experimentation, that secondary 

 sexual characters in insects, as well as certain primary organs, 

 such as those of copulation and oviposition, do not depend upon 

 the presence of gonads for their development. 



In Paracopidosomopsis I have found similar larvae, which 

 never undergo metamorphosis and are non-viable. In this 

 species the asexual embryos can be recognized in young polygerms 

 seventy to seventy- tw^o hours old. Figure 56 shows the youngest 

 stage that I have found. The young asexual embryo is distin- 

 guished from the other embryonic masses by two features of 

 its organization. It has a larger number of cells and the inner 

 membrane is relatively thicker than in the primary masses. 

 The embryonic cells multiply very rapidly and soon form a 

 solid spherical mass (fig. 57, As.E.). At the seventy-two hour 

 stage the asexual embryo gives evidence of differentiation, and 

 is surrounded by completed inner and outer membranes (figs. 

 53, 58, As.E.). It is frequently separated from the rest of 

 the polygerm. A single asexual embryo may frequently arise 

 during the primary mass stage of the polygerm, but it is 

 not the universal rule. In some pol^^germs of this stage no 

 asexual embryo is present. Furthermore, it frequently happens 

 that two or more asexual embryos may arise in a single polygerm 

 at this early period. Figure 72 shows two young asexual larvae 

 that must have started their development during the primary 

 mass stage. The polygerm shown in figure 73 has four asexual 

 embryos, all in the same stage of development, but situated at 

 different points in the polygerm. In figure 56 the asexual em- 

 bryo has arisen at the side of the polygerm; in figure 57, at the 

 anterior end, and in figure 58, at the posterior end. All of these 

 facts show that in Paracopidosomopsis an asexual embryo may 

 arise at any point in the young polygerm, and not habitually 

 from the posterior region of the egg, as reported for Litomastix 

 by Silvestri. 



