22 SUPPOSED CASES OF 



reared several young females of Agelena labyrinthica, Tegenaria 

 domestic** and Tegenaria civilis in a perfectly isolated condition, 

 and imprisoned in transparent glasses ; when these, after years 

 of care and feeding, had become full-grown, they laid eggs in 

 their virgin state, from which no brood was evolved. 



The negative results obtained by these direct observations of 

 themselves furnished a sufficient ground for doubting the cor- 

 rectness of the cases of pretended Parthenogenesis above referred 

 to ; but the most convincing proof that observations of this kind 

 in general, which are only made by accident, and not designedly 

 contrived, must be received with the greatest distrust, as on such 

 occasions mistakes so easily slip in, is furnished by the following 

 epistolary communications. I am indebted to Herr W. von 

 LangsdorfF, of Lahr, for the following note: "A female of 

 Gastropacha Quercus was evolved, which I took out of the 

 breeding-cage standing in my garden and carried into my 

 cabinet, which lies behind two rooms, where I placed it in an 

 open box ; the doors stood half open, as it was the height of 

 summer and very hot ; when I returned some time afterwards, 

 I found this female Bombyx in copulation with a male, which, 

 however, flew away swiftly on my arrival ; this female of course 

 laid fertilized eggs, whilst other females of G. Quercus which 

 were excluded soon afterwards, and which I had carefully im- 

 prisoned, certainly laid eggs, but these subsequently shrivelled 

 up, as they were unimpregnated. Now, had I come a little later, 

 when the male had already flown away, I should probably have 

 been deceived also, as the female Bombyx was in exactly the same 

 position as that in which I had placed it, and I could not have 

 supposed that a male Oak moth could slip so unperceived through 

 two rooms, in which there were several persons at the time, into 

 a third." Herr von Heyden wrote me a little while ago : " It is 

 remarkable, besides, with what acuteness certain male moths 

 scent out their females. Many years ago I saw a number of 

 males of Psyche pulla swarming about a closed window in my 

 sitting-room, and some of them settling on the panes. My 

 attention being attracted by this, I perceived that females of this 

 species had been evolved in a box standing in the room near the 

 window. I was acquainted with no locality for this species in 

 the neighbourhood of my dwelling." How easily, even in this 



