1136 General Notes. ' [November, 
organs. The two median rows of nerve-cells are faintly browned 
with osmic acid, while the four rows of nephridial cells are deeply 
browned, forming thus a sharp contrast in color. The two lateral 
ward into the fully outlined ganglia. The same has been done 
on sections, leaving no doubt as to the origin of the nerve system 
of the trunk. Iam not able to say whether the two rows o 
nerve-cells extend into the cephalic lobe; but I am certain that 
the nerve-collar, including the supra-cesophageal ganglia, is formed 
from cells that lie beneath the epidermis, and not from a thick- 
ening of the epidermis itself. 
The epidermis overlying the nerve-cells destined to form the 
four sub-cesophageal ganglia, thickens up at an early date and 
eventually becomes from two to three or more cells deep. This 
thickened portion of the epidermis has nothing whatever to do 
with the formation of any part of the nervous system. The deeper 
cells of this thickening form provisional gland-cells, which serve 
to sea the embryo, after its escape from the egg-membrane, to 
the ventral side of the parent. In this manner the young are 
carried ace until the posterior sucker is developed sufficiently 
to serve as an organ of attachment. These gland-cells are colored 
dark brown, and are thus very easily distinguished from the 
lighter-colored nerve-cells lying beneath them 
he epithelium of the whole alimentary tract, excluding the 
stomodzeum (pharynx) and proctodzum, which are derived from . 
the epidermal layer, arises from free nuclei belonging to the three 
large blastomeres (a2, 4 andc in my figures). The cells which 
form the cesophagus are the firstin order of development, making 
their appearance just beneath the stomodzal thickening, in the very 
earliest stage of the germ-bands. From the mass of cells formed 
at this point arise not only the cesophageal epithelium, but also 
the salivary glands. The method employed gives preparations in 
which all the embryonic tissues of the head and anterior portion 
of the trunk (epidermis, larval gland, salivary glands, nerve-cells, 
muscle-cells, and cesophageal epithelium) are distinguishable. 
The cells destined to form the epithelial lining of the stomach 
arise later than those of the cesophagus. They appear first as 
ret cells, on the ventral side, at the anterior end of the future 
dorsal line, I find no fully formed endoderm cells (except salivary 
ells), but do find free nuclei in the anterior half. 
-O of the i arise as bulb-like thickenings of 
