29 



a former Course of Lectures on the subject of Generation, 

 nine years ago, and every exact observation and experiment 

 subsequently recorded serve to render that hypothesis less 

 tenable and more gratuitous. 



The learned and ingenious authors of the deservedly 

 popular e Introduction to Entomology 5 admit it to be "an 

 incontestable fact that female Aphides have the faculty of 

 giving birth to young ones without having had any inter- 

 course with the other sex/' and they suppose "that one 

 conjunction of the sexes suffices for the impregnation of 

 all the females that in a succession of generations spring 

 from that union." They adduce, in order to show that 

 such a supposition is not contradictory to the general 

 course of nature in the production of animals, the case of 

 the hive-bee, " in which a single intercourse with the male 

 fertilizes all the eggs that are laid for the space of two 

 years ;" and the case of a common spider, showing (e that 

 the sperm preserves its vivifying powers unimpaired for a 

 long period, indeed a longer period than is requisite for the 

 impregnation of all the broods that a female Aphis can pro- 

 duce.^ But these instances do not touch the question how 

 one of such a brood, insulated from all connection, should 

 give birth to other broods. Admitting that this pheno- 

 menon may depend on the inheritance of the impregnating 

 principle transmitted from generation to generation, the 

 problem for the natural philosopher to explain is, how this 

 is brought about. The superaddition of the { spermatheca *' 

 to the vagina of the queen- bee, as of other oviparous in- 

 sects, plainly accounts for the fact in the ceconomy of that 

 insect which Messrs. Kirby and Spence quote, according 

 to the function of the part determined by the well-devised 

 experiments of Hunter on the silk-moth*. To say that one 

 conjunction of the sexes suffices to impregnate the females 

 of the successive generations of Aphides springing from that 

 union, is little more than a statement of the fact ; and it 

 * On Bees,, Philos. Trans. 1792, p. 175. 



