4500 Insects. 



— to put forth this view, 1 say, is to advocate a doctrine in physiology 

 as mischievous as it is deeply erroneous. I think, therefore, that the 

 doctrine of Steenstrup may prove to be unfounded as far as it would 

 involve, intrinsically, new phenomena in the processes of reproduc- 

 tion; and, as I have said on a preceding page, all its conditions may 

 find their illustration and solution in the various phases of gemmi- 

 parity. 



If, in this discussion of some of the highest relations of physiology, 

 we have not wandered too far from our subject proper, which we have 

 thereby sought to illustrate indirectly, we will revert to the thread of 

 its discourse for a few concluding remarks. 



The final question now is, what is the legitimate interpretation to 

 be put upon the reproductive phenomena of the Aphides we have 

 described ? My answer to this has been anticipated in the foregoing 

 remarks. I regard the whole as constituting only a rather anomalous 

 form of gemmiparity. As already shown, the viviparous Aphides 

 are sexless : they are not females, for they have no proper female 

 organs, no ovaries and oviducts. These viviparous individuals, there- 

 fore, are simply gemmiparous, and the budding is here internal instead 

 of external as in the Polyps and Acalephs ; it moreover takes on some 

 of the morphological peculiarities of oviparity ; but all these dissimi- 

 lar conditions are economical and extrinsic, and do not touch the in- 

 trinsic nature of the processes concerned therein. 



Viewed in this way, the different broods of Aphides cannot be said 

 to constitute as many true generations, any more than the different 

 branches of a tree can be said to constitute as many trees ; on the 

 other hand, the whole suite, from the first to the last, constitute but a 

 single true generation. I would insist upon this point as illustrative 

 of the distinction to be drawn between sexual and gemmiparous re- 

 production. Morphologically they have, it is true, many points of 

 close resemblance ; but there is a grand physiological difference, the 

 true perception of which is deeply connected with our highest appre- 

 ciation of individual animal life. A true generation must be regarded 

 as resulting only from the conjugation of two opposite sexes — from a 

 sexual process in which the potential representations of two indivi- 

 duals are united for the elimination of one germ. This germ -power 

 may be extended by gemmation or by fission, but it can be formed 

 only by the act of generation, and its play of extension and prolonga- 

 tion by budding or by division must always be within a certain cycle, 

 and this cycle is recommenced by the new act of the conjugation again 

 of the sexes. In this way the dignity of the ovum as the primordium 



