478 INSECTA. 



the male had united himself with her, and found the penis in the open- 

 ing of this bag ; and by opening the duct where the penis lay, I observed 

 the semen lying on the end of the penis. In another I observed the 

 bag to fill in the time of copulation ; and in a pair that died in copula- 

 tion, on examining them, I found the end of the penis in this bag 1 . 



When we consider all appearances with regard to the parts them- 

 selves, we shall find several singularities. First, many of the ova 

 are completely formed, and covered with a hard shell before copulation, 

 and a vast number are laid after the first copulation; secondly, the 

 sexes are a vast while in copulation ; thirdly, the bags at the anus are 

 filled at the time of copulation. 



From the first observation, it appears that the egg can receive the 

 male influence through its hard or horny shell, and that one copulation 

 can impregnate a vast number of eggs. To know how far the whole 

 or only part of the eggs were impregnated by each copulation, I took a 

 female just emerged out of its cell and put a male to her, and allowed 

 them to have their full time. They were in copulation ten hours. I 

 then put her into a box by herself, and numbered the different parcels 

 of eggs as she laid them, viz. 1, 2, 3, 4, and 5. These eggs I pre- 

 served, and, in the summer following, I perceived that the parcel No. 5 

 was as prolific as the parcel No. 1. So that this one copulation was 

 capable of impregnating the whole brood; and therefore the male 

 influence must either go along the oviduct its whole length, and impreg- 

 nate the incomplete as well as the complete eggs, which appears to me 

 not likely ; or the eggs not yet formed might be impregnated from the 

 reservoir in the act of laying. For I did conceive that these bags, by 

 their containing semen, had a power of impregnating the egg as it 

 passes along to the anus, just as it passed the ducts of communication. 



Experiments on impregnation. — Finding from the last experiment 

 that eggs completely formed could be impregnated by the semen, I 

 wanted next to see if they could be impregnated from the semen of 

 this bag ; but I conceived it proper first to see whether the ova of 

 insects might be impregnated without the natural act of copulation by 

 applying the male semen over the ova just as they were laid : the "fol- 

 lowing experiments were made on the silk-moth. 



Experiment 1. — I took a female moth as soon as she escaped from her 

 pod, and kept her carefully by herself upon a clean card till she began to 

 lay. I then took males that were ready for copulation, opened them, 

 exposing their vesiculse seminales, and after cutting into them, collected 

 their semen with a camel-hair pencil, with which I covered the ova as 

 they passed out of the vagina of the above female. This card had a 

 1 [Hunt. Prep. Phys. Series, No. 2850.] 



