226 H.\ROLD R. HAGAN 



not shown that in any other insect the indiisiinn attains such 

 development. On the other hand, we should expect this organ 

 to be present in more or less rudimentary form in a few, at least 

 of the other orthoptera. Indeed, such is the case in Orchelimum 

 vulgare where the de^'elopment of the organ closely approaches 

 that of Xiphidium, while in Stagmomantis a small group of cells 

 immediately anterior to the germ band probably represents a 

 more rudimentary type of indusium than I figure for Parateno- 

 dera sinensis. l\vo well developed indusial structures have 

 been described by Muir and Kershaw^ ('12) for one of the Homop- 

 tera. They find that the embryo of Siphanta acuta possesses 

 an outer indusium adhering to the inner surface of the serosa. 

 It completely surrounds the yolk and embryo. A second indu- 

 sium is closely applied to the yolk and is fused to the edges of the 

 amnion. It does not cover the amnion or the embryo. That 

 the structure in the mantids has escaped notice so universally 

 can be readily understood if it chanced to occupy a position 

 similar to its location in P. sinensis where it is usually torn off 

 with the embryonic envelopes while the embryo is being pre- 

 pared for staining and mounting. 



As early as the stage shown in figure 10 there is a very compact 

 mass of cells lying in the serosa just above, or a little posterior 

 to the cephalic third of the ventral plate. In the later stages 

 (figs. 11, 12) this area is shifted posteriorly until it lies over 

 the last mandibular or the first thoracic metamere. The cells 

 of the serosa are very much flattened so that each covers con- 

 siderable area, while the indusium remains compact and dis- 

 tinctly columnar as is seen in sagittal section (text fig. 2, A). 

 The nuclei are uniformly situated at the bases of the cells which, 

 at their upper ends, appear alveolar in structure and apparently 

 are attached firmly to the vitelline membrane. This is the same 

 stage as seen in figure 2. 



It has been shown in Xiphidium that, after segmentation 

 occurs, the embryo moves toward the posterior pole in its in- 

 vagination and passage through the yolk to the dorsal surface 

 of the egg. This movement separates the embryo from the 

 indusium and leaves the latter free. It is only after such separa- 



