Page:The Effect of External Influences upon Development.djvu/70

66 but such abnormalities are never due to a general insufficiency of nourishment. They may depend, as E. Ziegler shows (Lehrbuch der path. Anat. 1892, p. 369), either on the transmission of abnormal primary constituents of the germ, on primary pathological variations of the germ, or on external injuries: thus, for instance, a constriction of the limbs of the embryo by the umbilical cord or the egg membranes may occur.

NOTE XIV (p. 43).

Until lately it had only been demonstrated in the case of bees that food differences determined whether the female larvae should become workers or queens. The quality and quantity of the food which the different kinds of bee-larvae receive is accurately known, chiefly owing to the beautiful researches of Planta. In the case of ants there is a lack of evidence; but very valuable and definite infomation has recently been obtained on this point as regards termites, concerning which we were previously very ignorant. Grassi and Sandias's observations in Catania ('Costituzione e sviluppo della Società dei Termitidi. Osservazione sui loro costumi etc.'; Catania 1893, Atti dell' Acad. Gioenia di Sc. nat. Vol. VI e, VII) have shown that, in the Sicilian termites, the egg, like that of the bee, contains the primary constituents of each kind of individual. Whether the development of the male is determined by the absence of fertilization must still be left an open question; but it has been definitely established that the larvae of the fertile females receive far more abundant and more nourishing food than do the young which will give rise to workers or soldiers. Moreover, even at a later stage, the larvae can at will be reared either as fertile forms or as barren workers or soldiers; and here again it is a nutritious secretion of the insect itself which leads to the production of the sexual form. just as in the case of bees, the larvae for three days are all fed with this nutritive secretion, after which time only those which are destined to become sexual forms continue to receive it regularly, the