No. 2.] BLATTA AND DORYPHORA. 293 
peated washing in 70 per cent alcohol, preserved in alcohol of 
the same strength. Both methods gave equally good results. 
Though I have succeeded in dissolving the chitin of the 
odtheca with sodium hypochlorite, the method of tearing off 
the walls after heating to 80°C. gave such satisfactory results 
that I adhered to it throughout my work. 
I have found Grenacher’s borax carmine in every way the 
most expedient and reliable staining fluid. Eggs and embryos 
up to the time when the cuticle develops were stained before 
imbedding in paraffine; the sections of other embryos were 
stained on the slide after attaching them with Mayer’s albumen 
fixative. 
The clusters of bright yellow eggs of the potato-beetle (Dory- 
phora decemlineata, Say) may be found on the under surfaces of 
the leaves of the potato-plant during the whole summer, as the 
insect is polygoneutic. 
The beetles, frequently found copulating, may readily be kept 
in confinement, and will deposit their eggs in the typical flat 
clusters on the walls of any box or vessel in which they are kept. 
As I commenced collecting material late in the season, I did not 
keep the insects in confinement till they oviposited, but collected 
the eggs from the plant. It was found convenient to cut out 
the piece of the leaf to which the egg-cluster was attached and 
to keep it by itself during the process of preparation, as all the 
eggs of a cluster are in almost exactly the same stage of de- 
velopment. 
Beautiful results in preparation were obtained by heating the 
eggs to 80°C. for 10 minutes in Kleinenberg’s picrosulphuric 
acid (with 3 volumes of water) and preserving in 70 per cent 
alcohol. 
By this process the envelopes, which in the fresh egg adhere 
closely to the yolk, dilate and stand off from the surface of the 
egg, and except in the very youngest stages can be rapidly and 
easily removed with the dissecting needles. 
A great number of eggs, heated to 65°C. only, or hardened 
in cold Perenyi’s fluid, corrosive sublimate or simple alcohol, 
proved to be useless, as the envelopes adhered firmly to the sur- 
face of the yolk. 
The hot picrosulphuric acid fixes the cells of the embryo in a 
most satisfactory manner; enough details of the karyokinetic 
