115 



Generation has been divided into two classes, — i. Single or 

 equivocal generation ; and 2. Double generation or propagation. 



Double generation or propagation was of three descriptions, — i. 

 A portion of the old individual might be separated and become an 

 independent being, which was called propagation by shoots. 2. In 

 the body of the old individual the commencement of a new one might 

 be spontaneously developed, which germen, having attained its 

 maturity, quitted the maternal sphere and maintained a separate 

 existence, which was called propagation by germens. 3. The usual 

 method of propagation by the development of the germ by the re- 

 ception by the mother by intromission of a peculiar exciting fluid. 



The last method of propagation was called sexual. The active 

 individual or portion was called the male, and that upon which it 

 acted, the recipient or germ-forming individual, the female. 



Where these two faculties were united in one individual it was 

 then called Hermaphrodite ; an abnormal state of organism to which 

 he would allude more particularly afterwards. 



On the subject of single or equivocal generation he had but little 

 to say. By means of it only the very lowest order of organism was 

 produced. The best known instances of generation by this means 

 occurred in that of a particular species of louse, which originated upon 

 the skin and collected in great numbers at particular spots . 



Certain species of acari were also developed in the same 

 manner. 



Professor Burmeister says : — " The second kind of propagation, 

 that by shoots, has not yet been observed in insects ; it is also perfectly 

 contradictory to the idea of creatures so highly organised as they are. 

 Some observations, however, seem to confirm the possible development 

 of insects from £enne;is or c^gs laid by an unimpregnated female." 



Subsequent investigation and researches had proved that not only 

 was such a mode of development (as the last named) possible, but that 

 il was of not unfrequent occurrence. This mode of propagation by 

 germens constantly and regularly took place in certain genera. In 

 others it occurred only occasionally. As a regular mode it was ascribed 

 to the Aphides, or plant lice. These produced throughout the summer 

 living female young ones, which again, without any preceding impreg- 



