414 The American Naturalist. [May, 
been going on unseen in the colorless living protoplasm of the 
The eggs of our Shrimp are taken at short intervals during 
several days or weeks, so that the series will represent the whole 
history of growth from the o^^^ to the young prawn. The ova 
are then killed and hardened by suitable reagents, and finally 
preserved in alcohol. They are then stained with certain dyes 
like carmine, haemotoxylon, or osmic acid (which both kills, 
hardens, and stains protoplasm at the same time). A great 
step was taken in modern biology (and especially embryology) 
when it was discovered that protoplasm has such a remarkable 
affinity for the aniline and vegetable dyes. The colorless and 
invisible can be made to yield the secret of hidden change in 
colored pictures. Furthermore it is probable that certain 
kinds of protoplasm, or protoplasm in certain stages combines 
only with particular dyes. 
The stained eggs are then saturated with parafifine and em- 
bedded in a block of this substance. The paraffin block is 
clamped in the holder of a microtome, an instrument for cut- 
ting very thin sections, and then, thanks to the property of the 
paraffine, each section, as soon as cut by the passage of the 
knife, adheres by its edge to the section following, so that 
a paraffine ribbon can be cut, a yard long if necessary, in which 
the embedded &%<g will now appear in the form of a series of 
very thin colored sections, arranged in serial order. It is then 
a simple matter to fix them upon a glass slide, to remove the 
paraffin, and to seal the whole in a drop of balsam. Thus may 
we bring out the hidden writing and read the secret manu- 
We have not the time to follow in any detail the life history 
of an animal like the Shrimp, however interesting it might be, 
to see how from the simpler the complex arises, how the adult 
with its tissues and organs each so remarkable and often com- 
plicated in itself, arises from comparatively simple beginnings, 
and how the individual in its own life history repeats in an ab- 
breviated and modified form, the history of the race. But we 
do well if we realize this wonder of wonders, the development 
