480 INSECTA. 



discharge the ova, might at the same time force the semen into the 

 vagina, and so impregnate them. It may be observed that the first 

 eggs that were laid stuck faster to the card, while the latter did but 

 slightly, and the last not at all. This would prove that the bag serves 

 to secrete a fluid to attach the ova as well as a reservoir for the semen, 

 and that they first received this fluid from the duct of the bag. 



To know whether one act of coition would impregnate the whole ova 

 in a female silk-moth, I made the following experiment. 



Experiment 5th. — I took a female as soon as it had escaped from its 

 pod, and, when fit for copulation, I allowed a vigorous male to copu- 

 late freely. I then put her upon a clean card, where she laid all her 

 eggs, viz. three or four hundred, numbering the parcels of eggs as they 

 were laid. In the ensuing season the whole proved to be impregnated. 

 They hatched irregularly, for some of the last laid, hatched as soon as 

 those that were first. The experiment shows that one act of copula- 

 tion is sufficient to impregnate the whole ova. 



Experiment 6th. — To see whether it was necessary for impregnating 

 the whole ova to allow the male to copidate the usual time (which is 

 about seventeen hours), I allowed a vigorous male to copulate with a 

 female for ten minutes, which is about -gL of the usual time, the ova 

 being carefully kept till the ensuing season. None hatched. 



Experiment 1th. — Finding that the bag which contained the male 

 semen was small before impregnation, and that it got gradually larger 

 in time of coition, I made two moths copulate, and as soon as they were 

 together, cut open the female and exposed this bag, which is of a plain 

 uniform sbining surface, hard, and rather of a whitish colour; after 

 the act had continued for some time, I thought I perceived the bag 

 gradually getting larger, but so slowly as to be hardly perceivable. I 

 tben opened another female about two hours after; and, on comparing 

 these bags, the difference was very evident ; but the pain in which the 

 female was, occasioned violent exertions, and they separated. I now 

 observed the penis of the male, and found that there was a whitish 

 ropy fluid oozing from the end of it, wbich continued for some time ; 

 and on comparing it with the fluid in the female reservoir, found it 

 exactly similar in consistence, colour, &c. 



The eggs of the silk-worm are of that class that are laid one year 

 and hatched in the following. As there is sufficient summer after being 

 laid for their hatching the same season, it would appear that they 

 required a certain time after laying, or impregnation, to become perfect. 

 What time is required is not to be known without an experiment. It 

 is certain, however, that it requires a longer time than the remaining 

 warmth of the same season of laying. But in case the autumn of the 



