18 
PROGRESS OF MICROSCOPICxiL SCIENCE. 
the flank of the creature, then curves back towards the ventral surface 
and opens into the lateral vessel. There are, consequently, numerous 
capillary ramifications, exceptional amongst the nemertians, hut recall- 
ing the arrangement described by M. Blanchard in Cerehratulus 
Liguricus ” “ The structure of the highly developed proboscis neces- 
sitates the establishment of a special genus for these nemertians;” 
and M. Marion adopts the name “ Drephanophorus ” proposed by Mr. 
Hubrecht. 
The Character of the Starch-granule . — Professor Harrington, in a 
paper in the ‘ American Naturalist ” for April, says that if we take a 
little of the starch from the potato and dry it, without the addition of 
water, at a temperature of perhaps l"jO°, we shall see a dark point 
appearing at one end — usually the smaller. This is the nucleus, and 
around it are arranged concentric rings. It has been described as a 
little pedicle or stem by which the starch-grain is attached to the cell- 
wall. This was when it was still thought that the grains budded out 
from the wall, a theory completely disproven now, by what is known of 
the development and functions of the wall, as well as by specific obser- 
vations on the formation of the grains themselves. The nuclei have 
been described too as holes, passing into the interior from the outside, 
and admitting the materials from which the successive layers were 
formed from without inwards. If the development of the starch- 
grain were endogenous, there might be some ground for this hole- 
theory of the nucleus, but it is now well proven that their formation 
is from within out, or exogenous. There is no easily accessible 
specimen at this season of the year to illustrate this, but writers 
generally refer to ripening corn, w r here all the stages can sometimes 
be seen in a single grain. However, we can easily prove with the 
specimens under examination that the nucleus is neither a little stem 
nor a canal. If it were either, it would appear, as we roll the grains, 
sometimes elongated. As we roll the grains over, by inclination of 
the stage, or pressure from one side, as before, we see no difference in 
the shapo of the nucleus. It is the same round or angular black spot, 
occupying the same position from whatever point it is viewed. If wo 
are lucky, we may get a grain up on end, and examine it in the direc- 
tion of its long diameter. The position of the nucleus and arrange- 
ment of the rings remain the same. 
What can we conclude concerning the nature of the nucleus from 
this ? It w r as indistinctly or not at all visible in the fresh grain ; it 
becomes visible on drying, and looks like an air space. It is in the 
structural centre of the grain. If the drying is carried far enough, 
cracks may be seen extending from the nucleus. They generally 
radiate, looking something like a star. Sometimes one long crack 
runs the greater part of the length of the grain. The cracks may 
and may not reach the surface. Taking all these facts together, we 
can draw the fair conclusion : that the layers differ in density ; that 
the inner layers are softer than the outer, because they contain succes- 
sively more water ; that the water is driven off by the heat and the 
consequent vacuity appears, forming the “ nucleus,” where there is 
most w r ater, that is, in the innermost layers ; that farther drying 
