VOL. LXXXII.] PHILOSOPHICAL TRANSACTIONS. 18/ 



of this I shall now give an explanation in the silk-moth, which may be applied to 

 the bee, and many other insects. 



In dissecting the female parts in the silk-moth, I discovered a bag lying on 

 what may be called the vagina, or common oviduct, whose mouth or opening 

 was external, but it had a canal of communication between it and the common 

 oviduct. In dissecting these parts before copulation, I found this bag empty, 

 and when I dissected them after, I found it full. Suspecting this to contain the 

 semen of the male, I immediately conceived the following experiment: I opened 

 the female as soon as the male had united to her, and found the penis in the 

 opening of this bag, and by opening the duct where the penis lav, 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 the act, I found the penis in 

 this passage. 



When we consider the impregnation of the egg in the silk-worm, we may 

 observe the following circumstances: first, many of the ova are completely 

 formed, and covered with a hard shell, before copulation ; 2dly, the animals are 

 a vast while in the act of copulation; and 3dly, the bags at the anus are filled 

 during the time of copulation. From the first observation it appears, that the 

 egg can receive the male influence through the hard or horny part of the shell. 

 To know how far the whole, or only a part of the eggs, were impregnated by 

 each copulation, I made the following experiments.* I took a female just 

 emerged out of her cell, and put a male to her, and allowed them to be con- 

 nected their full time. They were in copulation 10 hours. I then put her into 

 a box by herself, and when she laid her eggs, I numbered the difl'erent parcels 

 as she laid them, viz. 1, 2, 3, 4, 5; these eggs I preserved, and in the summer 

 following I perceived that the N° 5 was as prolific as the N° 1 ; so that this one 

 copulation was capable of impregnating the whole brood: and therefore the male 

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

 incomplete eggs as well as the complete, which appears to me not likely; or 

 those not yet formed were impregnated from the reservoir in the act of laying: 

 for I conceived that these bags, by containing semen, had a power of impreg- 

 nating the egg as it passed along to the anus, just as it traversed the mouth of 

 the duct of communication. 



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

 and also finding that the before-mentioned bag was a reservoir for the semen till 

 wanted, I wished next to discover if they could be impregnated from the semen 

 of this bag; but as this must be done without the act of copulation, I conceived 

 it proper, first, to see whether the ova of insects might be impregnated without 



* All these experiments on the silk-moth were begun in the summer 1767, and repeated by Mr. 

 Bell in the year 1770. — Orig. 



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