186 Dr. Wallace on 
some already naturalized, some undergoing the process of accli- 
matization. These new and valuable species have been brought 
some from the far East, some from the far West, many thousands 
of miles during their stages of torpidity, a result possible only 
through the rapid transit afforded in the present day by the aid of 
steam; they vary much in their habits and economy, but are 
mostly hardy, requiring out-of-door culture ; their cocoons differ 
much in shape, size and in quality of the silk from the cocoon of 
B. Mort, and they require a far different treatment, both during 
their growth, and subsequently, for the purpose of unwinding the 
thread from the cocoons and reeling it into a compound thread 
fit for the manufacturer. 
The cause which has led to the search for and the introduction 
of new species of silkworms into Europe is the great failure in 
the crop of cocoons of the B. Mori, owing to a disease called 
‘‘ La Gattine,” which has raged epidemically in the silk-producing 
districts for the last ten years or more. In illustration of the 
great loss caused by this disease, I quote from “The Times” of 
Sept. 25th, 1865, as follows: “In Tuscany the silk crop is now 
gathered in and the result is ascertained; last year 55,000, this 
year 42,000 kilogrammes of cocoons are harvested. Previous to 
the disease 480,000 kilogrammes were annually gathered, and, as 
more mulberry trees have since been planted, the average ought 
now to have been 500,000 kilogrammes. The silk crop in the 
valley of Niceola, a province of Lucca, is better than last year, 
the cocoons being from seed procured from the island of Sardinia 
and some from Japan.” 
In order therefore to replace the loss caused by the ravages of 
this epidemic (for which there is known no remedy), the French 
government commissioned M. Guérin-Méneville, an able and per- 
severing investigator of natural science, Ist, to introduce new races 
of the B. Mori from its original habitat, in order to strengthen, 
by reverting to the old stock, the constitution of the silkworm, 
which was supposed to have become deteriorated by European 
residence and treatment; 2ndly, to suggest means, if possible, 
whereby the ravages of the epidemic might be lessened ; and, 3rdly, 
to introduce and naturalize other and hardier species of silk-pro- 
ducing Bombyces. Under the immediate surveillance therefore of 
this distinguished naturalist, experiments have been carried on in 
various parts of France by a band of zealous and spirited co- 
operators, and more especially by permission of the Emperor in a 
laboratory at the Imperial Farm of Vincennes, where the soil is 
of the lightest and most sterile character. These experiments 
have already resulted in the acclimatization of two new species, 
