We have already alluded to the fact that in the Blattidae the eggs are laid in a capsule formed in the interior of the mother-Insect. This capsule is a horny case varying much in size and somewhat less in form in the different species; it is borne about for some time by the mother, who may not infrequently be seen running about with it protruding from the hinder part of the body. Sooner or later the capsule is deposited in a suitable situation, and the young cockroaches emerge; it is said that they are sometimes liberated by the aid of the mother. Mr. Brindley has found it very difficult to procure the hatching of the young from their capsules. [Illustration: FIG. 126.—Egg-capsules of European Blattidae. A, _Ectobia lapponica_; B, _Phyllodromia germanica_; C, _Heterogamia aegyptiaca_. (After Brunner.)] It is known that some Blattidae are viviparous. In the case of one such species, _Panchlora viridis_, it appears probable that the egg-capsule is either wanting, or is present in only a very imperfect form.[155] On emerging the young _Blatta_ is in general form very similar to the parent, though usually much paler in colour. After casting {230}the skin an uncertain number of times—not less than five, probably as many as seven—it reaches the adult condition, the changes of outer form that it undergoes being of a gradual nature, except that at the last ecdysis the wings—in the case of the winged species—make their appearance, and the terminal segments of the body undergo a greater change of form. What mutations of shape may be undergone by the thoracic segments previous to the final production of the wings has not apparently been accurately recorded, Fischer's opinion being evidently based on very slight observation. The little that has been recorded as to the post-embryonic development since the observations of Hummel[156] and Cornelius[157] will be found in the works of Brunner.[158] According to this latter authority, in the wingless species the terminal segments of the body have the same form in the early stages as they have in the adult state, so that this latter condition can only be recognised by the greater hardness of the integument. When tegmina or wings are present in a well-developed form in a Blattid, it is certain that the Insect is adult; and when there can be seen at the side of the mesonotum or metanotum a piece, however small, separated by a distinct suture, it may be correctly assumed that the individual is an adult of a species having only rudimentary alar organs. The adult female of the common _Stilopyga orientalis_ shows this phenomenon.