125 REVIEWS, TRANSLATIONS, AND SELECTED ARTICLES. 



Prance, as well as in Piedmont and Lombardy, that tte most eflfect- 

 ual means of restoring vigour to the silkworm stock, when this 

 becomes deteriorated (as shewn by a poorer yield of silk, less numerous 

 eggs, &c.), is to employ what is called " virgin seed," or, in other 

 words, eggs laid by female moths that have been kept rigorously 

 from contact with the males. f^ome researches made on this 

 subject are published by M. Jourdan in the Comptes Rendus of 

 December 16, 1861. Although placing no great faith in the state- 

 ment in question, M. Jourdan determined to submit it to the test of 

 experiment. Three hundred worms (of the Briance variety) were 

 enclosed in separate boxes, each covered with a piece of guaze, of 

 which the ends were closely sewed together. These worms yielded 

 one hundred and forty-seven female, and one hundred and fifty-one 

 male moths. The latter were removed, and the females were kept 

 carefully imprisoned in their separate boxes. Out of the hundred 

 and forty-seven moths thus preserved, only six yielded really fertile 

 eggs. Two moths gave seven ; two others, three ; one, five ; and 

 one, two. These twenty-nine eggs, out of the whole number laid, 

 and kept enclosed as above stated, were all that came to life. Some 

 others, it is true, passed from the clear yellow into the greyish 

 stage, after the manner of fertile eggs, but these finally proved 

 abortive. The total number of eggs laid in this experiment, amounted 

 to about 50,000 : so that about one egg only in two thousand proved 

 fertile. 



In a second experiment, conducted in the same manner, but on 

 another breed of silkworms (a Chinese variety), results of a much 

 more striking character were obtained. Fifty cocoons were enclosed 

 in separate boxes, as before. From these, twenty-three females and 

 twenty-six males resulted. Of the former, seventeen produced 

 fertile eggs. The most productive gave one hundred and thirteen, 

 and the least productive yielded twelve. The proportion of fertile 

 eggs to the total number laid, was about one in seventeen, or 530 in 

 9000. 



The occurrence of Parthenogenesis amongst the Lepidoptera, ap- 

 pears, then, to be certainly verified ; and this fact, as observed by 

 M. Jourdan, cannot be looked upon otherwise than as one of great 

 physiological interest, when we consider the advanced organization 

 of the class in which it has been thus shewn to occur. An extension 

 of these experiments, in order to test the duration of the peculiarity 



