A. Usual condition of the mulberry mass immediately after segmentation has been completed. B. Appearance 
of the nascent pseudembryo after the coalescence of the ultimate spherules of the germ-mass. C. Pseu- 
dembryo shortly before the rupture of the vitelline sac. 
In this case the development of the pseudembryo from the germ-mass resembles in 
every way the development of the embryo in most of the invertebrate groups ; on three 
occasions, however, during the examination of a series of eight or ten broods, a whole 
brood of embryos were evolved under somewhat different circumstances. The surface 
of the mulberry mass became somewhat looser and more transparent, and under slight 
pressure a large, somewhat darker and more consistent central nucleus was observed 
(Plate XXI Y. fig. 1). This nucleus increased in size from hour to hour, the peripheral 
portion of the contents of the vitelline membrane gradually liquefying and becoming 
absorbed into the nucleus. At length the oval outline of the pseudembryo might be 
traced through the flocculent mass of semitransparent semifluid yelk. The remainder 
of the yelk now became completely transparent and liquid, the embryo increased rapidly 
in size, and its form was more clearly defined through the wall of the vitelline sac 
(Plate XXIY. figs. 1-4). I believe, however, that this latter is an abnormal mode of 
development, depending probably upon imperfect aeration. 
Observed during the process of development within the vitelline membrane, the 
embryo is at first nearly regularly oval, and the surface appears to be uniformly ciliated. 
I have never met with an instance in which the embryo escaped in this condition. In 
all the cases which I have observed, the ciliated bands so characteristic of the pseud- 
embryonic form have made their appearance before the rupture of the vitelline sac 
(woodcut, C) ; and frequently the pseudembryo has become somewhat reniform, a de- 
pressed ciliated patch indicating the position of the pseudostome. The pseudembryo 
frequently, but not constantly, rotates slowly and irregularly within the vitelline sac, 
the rotation depending evidently upon 4he action of the cilia on the surface of the 
pseudembryo. Immediately after escaping from the vitelline membrane, the pseud- 
embryo is about *8 millim. in length, oval, slightly enlarged towards one extremity, and 
girded by four nearly equidistant transverse ciliated bands. It consists throughout of 
very delicately vacuolated sarcode, which becomes more and more consistent towards 
the periphery, where it forms a smooth firm surface, which is not, however, bounded by 
any definite membrane. Towards the centre the substance becomes more fluid, and is 
mdccclxv. 4 B 
