Note 81 — PART II. EMBRYOLOGY OF INSECTS

Korschelt and Heider state that no cellular embryonal membranes are present in Synaptera, Uljanin finding none in the Podurids. In the embryo of Isotoma walkerii we, however, observed a membrane which we compared to the larval skin of many Crustacea, and both Sommer and Lemoine have detected in eggs of the same group a cuticular larval skin which is provided with spines for rupturing the chorion. The amnion is also wanting in Proctotrupids (Ayers), and is rudimental in Muscidæ (Kowalevsky, Graber), in viviparous Cecidomyidæ, according to Metschnikoff, who also states that in certain ants of Madeira the envelopes are represented only by a small mass of cells in the dorsal region.