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J. D. F. GILCHRIST. 
(8) Excretory matter in the form of dark specks and 
elongate rods is formed during this process and constitutes 
the characteristic pigment of the late embryos and larvae. 
(9) The ventral thickening of the ectoderm is found at an 
early stage. 
(10) The endoderm appears under the ectoderm, first as a 
number of cells at the anterior end, and ultimately as a com- 
plete chain of cells extending over the inner yolk, except at 
the point of proliferation at the posterior end. 
(11) The cells occupying the blastocoele break down like 
the outer cells, and become a mass of yolk granules, in 
which are scattered a number of nuclei with associated proto- 
plasm. 
(12) Some of these pass outward to form the endoderm, 
others pass inwards to form vitellophags. 
(13) A lumen is formed in the yolk mass and it becomes 
connected to the posterior involution, giving rise to a gastrula- 
like structure. 
(14) The internal mass of yolk assumes the form of a 
number of yolk columns or pyramids. 
(15) The posterior body cavities arise by a number of cells 
from the yolk mass forming a second layer under the endo- 
dermal layer. 
(16) The yolk lumen increases in size, the yolk granules 
becoming converted into a homogeneous substance. This 
takes place chiefly on the dorsal side, where the yolk lumen 
becomes connected with the archenteron. 
(17) The position and extent of the five body cavities in 
the larva are shown. 
(18) The yolk in the larva is in the form of an elongate 
mass of granules and homogeneous matter, lyiug on the floor 
of the archenteron. 
(19) Changes are described in the larval nervous system, 
and the appearance of a posterior thickening and involution 
of the ectoderm below the yolk mass is noted. 
