Prof. Owen,[16] indeed, goes so far as to say that the Orthoptera and other Homomorphous insects are, “at one stage of their development, apodal and acephalous larvæ, like the maggot of the fly; but instead of quitting the egg in this stage, they are quickly transformed into another, in which the head and rudimental thoracic feet are developed to the degree which characterizes the hexapod larvæ of the _Carabi_ and _Petalocera_.” [Illustration: FIG. 30, Egg of _Phryganea_ (Mystacides)—_A_¹, mandibular segment; _C_¹ to _C_⁵, maxillary, labial, and three thoracic segments; _D_, abdomen (after Zaddach). 31, Egg of _Phryganea_ somewhat more advanced—_b_, mandibles; _c_, maxillæ; _cfs_, rudiments of the three pairs of legs.] I quite believe that this may have been true of such larvæ at an early geological period, but the fact now appears to be, so far at least as can be judged from the observations yet recorded, that the legs of those larvæ which leave the egg with these appendages generally make their appearance before the body-walls have closed, or the internal organs have approached to completion. Indeed, when the legs first appear, they are merely short projections, which it is not always easy to distinguish from the segments themselves. It must, however, be admitted, that the observations are neither so numerous, nor in most cases so full, as could be wished. Fig. 30 represents an egg of a May-fly (_Phryganea_), as represented by Zaddach in his excellent memoir,[17] just before the appearance of the appendages. It will be seen that a great part of the yolk is still undifferentiated, that the side walls are incomplete, the back quite open, and the segments merely indicated by undulations. This stage is rapidly passed through, and Zaddach only once met with an egg in this condition; in every other specimen which had indications of segments, the rudiments of the legs had also made their appearance, as in Fig. 31, which, however, as will be seen, does not in other respects show much advance on Fig. 30.